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eismology is the study o Earths elastic vibrations, the sources that generate them,
and the structures through which they propagate. It is a geophysical discipline
that has a remarkable diversity o applications to critical issues acing society and
plays a leading role in addressing key scientic rontiers involving Earths dynamic
systems. Seismology enjoys quantitative oundations rooted in continuum mechanics,elasticity, and applied mathematics. Modern seismological systems utilize state-o-the-
art digital ground motion recording sensors and real-time communications systems,
and anyone can openly access many seismological data archives.
Seismologists keep their ear on Earths internal systems, listening or signals aris-
ing rom both natural and human-made energy sources distributed around the globe.
Tese seismic signals contain a wealth o inormation that enables seismologists to
quantiy active wave sources and determine structures and processes at all depths in
the planetary interior. Tis is done at higher resolution than is possible by any other
approach, revealing structures associated with dynamic processes that are active nowor have been ongoing over multibillion years. Recent breakthroughs in theory and data
processing now allow every byte o continuous seismological data acquired to be used
or imaging sources and structures throughout these dynamic systems, even extract-
ing coherent signals rom what had previously been dismissed as background noise.
Ground-motion recordings are intrinsically multi-use; seismic data collected to moni-
tor any specic Earth phenomenon, or example, underground nuclear tests, can also
advance studies o earthquake sources or deep Earth structure. Tis multi-use attribute
o seismic data places great value in the prevailing philosophies o open data access and
real-time data collection embraced by the U.S. seismological research community and
many o its international partners.
S
executiVeSummary
executiVe Summary
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Maintaining a healthy national research capability in seismology to pursue the many
societally important applications o the discipline and to address the 10 Grand Challenge
research questions requires sustained and expanded support o seismic data acquisition,
archival, and distribution acilities. Global and regional seismological networks with acommitment to long-term operation, and pools o portable instruments or shorter-
term land- and sea-based deployments, provide key observations essential to tackling
the Grand Challenges. Te Advanced National Seismic System (ANSS), the primary
earthquake monitoring system in the United States, must be completed. Te currently
sparse instrumental coverage o the vast areas o unexplored ocean oor needs to be
expanded. Source acilities or controlled-source seismic data acquisition are essential
to support crustal reection and reraction imaging, including marine airguns, explo-
sions in boreholes, and vibrating trucks. Cooperation among academic, government,
and industry eorts in controlled-source seismology must be enhanced to support the
Grand Challenge eorts. Completion o the planned deployment o the EarthScoperansportable Array across the conterminous United States and Alaska is important
or achieving the maniold science goals o that major NSF program. International par-
ticipation in open seismic data exchange or diverse seismic networks around the world
must be diplomatically pursued and expanded. Interdisciplinary workshops addressing
critical problems o the near-surace environment and deep Earth should be promoted,
with active seismological participation.
Many o the government and private sector users o seismology are now conronted
with serious workorce shortages. Expanded eorts are required to attract quantita-
tively oriented, diverse students to the discipline. Tese eorts should be abetted bybuilding on current education and outreach endeavors o the seismological community,
and by developing stronger partnerships among academic, industry, and government
laboratories, which are all impacted by workorce-shortage issues. At the same time,
some trends toward reducing seismological sta and resources in government labs need
to be reversed to sustain contributions o the discipline.
Seismology holds great promise or achieving major breakthroughs on the Seismological
Grand Challenge questions and associated societal benets over the next ew decades,
as long as ederal agencies and industry continue to invest in basic research programs
and inrastructure or this burgeoning geophysical discipline. With the well-established
practices o open data sharing, expanding eorts to share sotware and to develop
community models, and the multi-use aspect o all seismic data, bountiul return on
investments in seismological inrastructure and training is assured. As progress on the
Seismological Grand Challenges is made, the undamental understanding o Earths
dynamic systems that is gained will advance the sustainability and security o human
civilization, along with satisying our deep curiosity about how planet Earth works.
executiVe Summary
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resources. Seismology intrinsically provides unpar-
alleled resolution o physical properties in the inac-
cessible interior rom the crust to the core. Seismicimaging o ossil-uel-bearing geologic structures is
essential to discovering, exploiting, and managing
critical energy resources that power global civiliza-
tion. When nuclear testing moved underground dur-
ing the Cold War, seismology assumed a key role in
treaty verication and in remote monitoring o weap-
ons development programs.
With these new roles in hydrocarbon exploration and
national security monitoring eorts complementingearthquake studies and Earth structure research, seis-
mology rapidly grew into a major high-tech research
discipline. oday, global seismometer networks trans-
mit ground motion recordings rom around the world
in real time via satellite, microwave, or Internet telem-
etry to data analysis centers. Automated computer
processing o the accumulated seismic signals is per-
ormed by many government agencies and research
programs to produce rapid bulletins o global seis-micity and prompt inormation or disaster mitiga-
tion. Tese activities are essential or the continu-
ous monitoring o the Earth system, and there is still
much room or improvement o methodologies used
in many eorts. Large-scale deployments o land- and
sea-based instruments utilize both active human-made
sources and passive natural sources o seismic waves,
revealing multiscale structures o the crust and deep
Earth. Massive online data repositories reely provide
the data to scientists, enabling research and monitoringapplications across academic, government, and com-
mercial sectors. Te complexity o seismic wave pro-
cessing and modeling eorts combined with very large
seismic data sets has placed seismology as a primary
driver o high-perormance computing at universities,
national laboratories, and industry or many decades.
11/2008
JapanGSN U.S.Australia Germany ItalyFrance OtherCanada
International Federation of
Digital Seismograph Networks
introduction
t ss s p s p s -q -
ss ss i F d Ssp nws (FdSn), w s
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6
volcanic eruptions, explosions, mine collapses, rock
bursts, landslides) that have very long-term nega-
tive impacts on human lie, property, and inrastruc-
ture, near-real-time access to seismic data is also o
great importance. Whenever it is possible to transmit
ground motion data to open archives in real time, mul-tiple societal applications o the signals are enabled.
By its very nature, seismology is sensitive to many
active, dynamic processes happening today in Earths
dynamic systems, and the discipline has expanded its
scope to include detecting and characterizing numer-
ous aspects o environmental change and near-surace
processes, including ground-water distribution, glacial
motions, storm migration, the ocean wave environ-
ment, and ocean circulation. Much o modern Earthscience research addresses complex physical systems
that involve interaces among multiple disciplines,
and seismology oers powerul tools or remote sens-
ing o structures and sources that complement other
approaches. Tis central importance o seismol-
ogy is noted in many major scientic planning doc-
uments (e.g., BROES, 2001; IUGG, 2007), and a
suite o research community organizations (CIDER,
COMPRES, CSEDI, FDSN, IASPEI, IAVCEI,
IRIS, MARGINS, RIDGE, SCEC, UNAVCOall
A dening attribute o seismograms is that they are
simply records o ground motion as a unction o
time. Tus, seismic data recorded by a network o seis-
mometers or any particular purpose (e.g., monitor-
ing nuclear testing or earthquake hazard analysis),
intrinsically provide signals that are valuable or mul-tiple unrelated uses. One can equally well study Earth
structure, earthquakes, explosions, volcanic eruptions,
and other processes with the same seismograms.
Study o the diverse Earth systems requires glob-
ally distributed sensors and international collabora-
tions on data acquisition and exchange. Te multi-use
attribute o seismic signals places a great premium on
continuously recording ground motions over as wide
o a requency band as possible, archiving all record-
ings in accessible ormats, and openly sharing thedata between nations and institutions, no matter what
the original motivation was or deploying the seis-
mic instrumentation. Te U.S. seismological commu-
nity, and its international partners in the Federation
o Digital Seismograph Networks (FDSN), have
strongly ostered this ramework o open access to
seismic data, establishing data centers that are acces-
sible to all researchers. Because the data play criti-
cal roles in rapid evaluation o short-term changes in
Earths dynamic systems (e.g., earthquakes, tsunamis,
introduction
Cumulative Terabytes Archived by Network Type
through August 31, 2008
0
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70
80
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USArrayFDSNRegional DataPASSCALGSN
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7
acronyms are dened at the end o the report) engage
seismologists with synergistic disciplines in min-
eral physics, geodynamics, volcanology, geology, and
increasingly, oceanography, hydrology, glaciology, cli-
mate, and atmospheric sciences.
Tis centrality o seismology in Earth science and
global monitoring engages multiple U.S. ederal
agencies in supporting the discipline, including the
National Science Foundation (NSF), the United
States Geological Survey (USGS), the National
Oceanic and Atmospheric Administration (NOAA),
the Department o Energy (DOE), the Department o
Deense (DoD), the Federal Emergency Management
Agency (FEMA), and the National Aeronautics
and Space Administration (NASA). Tis diversityo supporting agencies has beneted the discipline
immensely, and reects the multi-use nature o seis-
mological data. U.S. seismology is deeply engaged
in international activities such as the International
Monitoring System (IMS) o the Comprehensive
Nuclear est Ban reaty Organization (CBO), and
the Global Earth Observations System o Systems
(GEOSS), placing the discipline in high-level, scien-
tically and politically inuential roles.
One sign o a healthy scientic enterprise is that it
is producing major advances and paradigm shits.
As maniest in this report, seismology is a dynamic
and energized eld, with a continually expanding
portolio o important contributions. Examples o
recent transormative developments in the discipline
include the ollowing:
Creation o the open-access online seismic data
repository o the Incorporated Research Institutions
or Seismology (IRIS) Data Management System
(DMS) has enabled prolierating discoveries and
new societal applications by many researchers. Tis
acility, which houses terabytes o seismic data, reely
delivers these data to the entire world, an approach
being emulated internationally.
Te availability and centralized maintenance o large
pools o state-o-the-art portable seismographs, such
as IRIS PASSCAL, has driven a new era o discov-
ery in seismic source and structural studies across
the discipline.
Te discovery o coherent inormation contained in
recorded seismic noise allows virtually every data
byte to be used or scientic application; entirely new
approaches to structural studies and investigations
o changes in the oceanic and atmospheric environ-
ment have emerged. Earths background vibrations
contain inormation about sources and structures
that was not recognized until recently.
introduction
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8
Te recent discovery o a continuous spectrum o
aulting behavior, ranging rom conventional earth-
quakes that rupture at great speeds (including super-
shear velocities) to slow earthquakes that involve
anomalously slow rupturessome so slow that the
sliding motion does not radiate detectable seismicwaves or is maniested in seismic tremorhas uni-
ed seismic and geodetic monitoring o ault zones
and may have undamental importance or rictional
sliding processes and earthquake hazard.
Te discovery o the predominance o large-scale
structures with anomalous elastic properties in the
deep mantle by imaging methods (e.g., seismic
tomography) has brought a paradigm shit to our
understanding o mantle convection and thermalevolution o Earths deep interior, with new empha-
sis on thermo-chemical dynamics.
Project EarthScope, a major research eort unded
primarily by NSF, is providing unprecedented spa-
tial coverage o seismic and geodetic observations
introduction
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9
across North America, revealing ne-scale crustal
and mantle structures that are divulging secrets o
continental evolution.
Te emergence o quantitative physics-based pre-
dictions o surace ground motions using realisticdynamic ault rupture models and 3D geological
structures has begun to transorm earthquake haz-
ard analysis, complementing the emergence o per-
ormance-based earthquake engineering.
Te discovery o remote triggering o earthquakes
and enhanced understanding o earthquake inter-
actions has provided new insights into the stress
changes that lead to earthquake initiation.
Te tsunami generated by the great 2004 Sumatra
earthquake reafrmed the catastrophic potential
o natural events and the need or early-warning
systems. Automated data collection and process-
ing are enabling near-real-time responses to earth-
quake occurrence, including seismic shaking and
tsunami-warning systems that have potential to
save many lives.
Te continued health and vigor o seismology requiresederal and industry attention to critical ounda-
tions o the discipline and expansion o the base
upon which uture advances can be built. Core needs
include sustaining and expanding data collection
and dissemination inrastructure, providing access to
high-perormance computational resources, attracting
and supporting diverse, quantitatively oriented stu-
dents to the discipline, and ostering interdisciplin-
ary collaborations to study complex Earth systems.
o clariy the critical unctions and potential contri-
butions that seismology can make and the inrastruc-
ture needed to achieve the ull span o possibilities,
the seismology community has identied 10 Grand
Challenge research questions or the next ew decades
and the associated inrastructure needs essential or
making progress on these topics.
introduction
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and pressures along ault zones play important roles
in rictional behavior, and seismological eorts have
succeeded in imaging uid distributions at depth.
Catalogs o the locations o massive numbers o tiny
to moderate earthquakes, accurate within tens o
meters, reveal diverse rictional behavior among aultsand along a single ault surace. Persistent alignments
o small earthquakes on aults have been discovered by
precise event locations, and many examples o virtu-
ally identical earthquakes recurring at the same loca-
tion on a ault have been studied. Global and regional
arrays o seismic stations and deep borehole seismic
instruments like those deployed in the EarthScope
SAFOD drill hole, provide recordings that capture
the initiation, growth, and termination o ault rup-
tures. Resulting kinematic and dynamic aulting mod-els constrain physics-based theoretical models that are
used to predict strong shaking, at least in a probabilistic
sense. Among the most exciting Earth science discov-
eries o the past decade have been the coupled phe-
nomena o slow slip events (detected geodetically) and
seismic tremor. Te slow slip process appears to repre-
sent a rictional behavior intermediate between that o
steady sliding and stick-slip earthquakes. Seismic aulttremor, a low-level seismic rumbling with extended
duration, correlates with slow slip in some environ-
ments and may be a superposition o many individual
subevents, but its nature is still being investigated.
Seismology has made great progress in the basic
understanding o how and where aults are likely to
ail, but there is currently no reliable method or pro-
ducing short-term warnings o an impending earth-
quake. Te insights gained have provided useul seis-mic hazard assessments or land-use planning, as
guidance or construction standards, and or planning
grand challengeS For SeiSmology
2
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13
or emergency response. Far more can be achieved by
enhancing our undamental level o observations and
understanding o the physics o earthquake ruptures,
ranging rom better prediction o ground shaking
variations, to expansion o early warning systems or
earthquake and tsunami hazards.
Sidebar2
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key QueStionS and iSSueS
What physical properties control diverse types o
ault sliding?
How does the relationship between local conditions
at a point on a ault and conditions over the whole
ault surace evolve?
Is there a preparatory stage or ault ruptures? How
do ruptures stop?
Are mechanisms o interplate and intraplate earth-
quakes dierent?
What rictional constitutive laws govern aulting
variability, and how are rictional properties dier-
ent or high-speed slip? What governs transitions
rom stick-slip behavior to steady sliding?
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14
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What is the undamental nature o high-stress
asperities (areas o high-slip in an earthquake) and
the cause o riction variations?
How is episodic ault tremor and slip related to
large earthquake occurrence?
How do earthquake rupture zones recoverand reload?
How do large and small earthquakes undamentally
dier, i they do?
Can rupture directions and associated ground
motions be anticipated based on material
properties?
a ns F Z h
What are the geometrical properties o ault distri-
butions and how do ault networks and ault sur-
aces evolve over time?
Can we orecast the spatial and temporal occur-
rence o earthquakes and accurately predict
their eects on ground motions and on the builtenvironment?
How quickly can the size o an earthquake be
determined and reliable shaking and tsunami warn-
ings issued?
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v s s q.
t s pp s vp s
p ps ss sps qs.
eqs vv psss p sp
p ss w svs sv .
m pss s s s -
, sss , , p -
s, s s psss
pss p. i s s v pv
s ps ss s -ps
q s w p v
s. W w s s
ps q s v - sps q ss. S s ps
psss qs s v ps
w v w sps p q ss
s p , w svs
s psps pv s pv ps.
t p q pss, s
sv s, q p -
p p. ev qs
p w p -
, s w sv p ss q p-
. t nw os h k ss
v w ss s p sv s
v, s -
s -
q ppss p
v v. i
ws qs,
s vs w s
s. i s s -
v ss-
pv-
s
q
s ss
w s v q
p s v v.
b vs 2008
W q c.
eq P P
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5
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Near-surace processes aect water, energy, and min-
eral resources at depths o meters to a ew kilometers.
Detailed knowledge o Earths near surace is there-
ore a crucial part o managing a sustainable environ-
ment or civilization.
Near-surace geophysics is undergoing explosive
growth because o societal interests in assessing the
impact o human activities on our environment.
Although the near surace is accessible to drilling and
excavation, those activities cannot provide the needed
temporal and spatial resolution and must be comple-
mented by near-surace geophysics to connect the
dots. Seismology provides a number o cost-eec-
tive and noninvasive near-surace imaging methods,
including the use o reracted, reected, and convertedbody waves, and surace waves to produce 3D and 4D
(time-varying) subsurace maps that have applica-
tions or hydrology, civil engineering, earthquake haz-
ard assessment, archeology, nuclear blast detection, and
many other critical issues.
Shallow seismic methods play a key role in determin-
ing a vast range o geotechnical properties that are
critical to the built environment. Depth to bedrock,
the load-bearing strength o shallow materials, and
the expansive potential o soils can all be estimated
rom the properties o seismic waves. Seismic stud-ies in conjunction with coring can be used to map
lateral changes in specic soil horizons beneath con-
struction sites. Te shear modulus o soils is a critical
engineering strength parameter or assessing the sta-
bility o embankments, buildings, and the oundations
o other structures, and it can be quantied by non-
invasive seismic shear-wave studies using controlled
seismic sources and/or background seismic noise. Te
extent, thickness, and volume o unstable slopes and
past landslides, and mapping weak horizons at theirbases, can be used to assess hazards and direct mit-
igation strategies. Microearthquakes along the sides
and bottoms o landslides can potentially be used as a
proxy to monitor creep using seismic methods.
0
2
4
6
8
10
12
14
0 5 10 15 20
140 340 540 740 940 1140 1340 1540 1700
Velocity (m/s)
NorthSouth
h-s (s s) ssss s ss -
s, qs
ps q . b s
p- s ss f-
. t f
w s
. (i
F. g, a.r. lv, r.g. P, c.a.
Z, g.l. Fz, 2006. Wv
p w -
s: VSP-s s, Geophysics,
71, h1h11, :10.1190/1.2159049.)
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u n eps m ds
Si
d
ebar
7
i -s ss ss (s) s p s v s s vp
s s. as sp s v, ss s v s qv s p-
s vs s psss ss s. ms , s pss ss ss
pss, qs, pss. Sw p vs pp v
s s ( sss s s p) s ss wv vss. (i
d.S. d, S.r. F, W.r. W, 2008. S ss c c, u, ps,Science, 321(5886):217, :10.1126/
s.1157392. rp w pss aaaS).
Double Couple
IsotropicImplosion
ExpandingCrack
CollapsingCrack
IsotropicExplosion
Nuclear and
other Explosions
Earthquakes
Crandall CanyonMine Collapse, UtahAugust 6, 2007
Cavity Collapses
Nuclear TestKimchaek, North KoreaOctober 9, 2006
DUG
O16A
P17A
P18A
Q16A
Q18A16 s
T R V
Crandall Canyon Seismograms
DUG O16A O18A
P18A
Q16AQ18A
100 km
grand challengeS For SeiSmology
Ss ps z
pss s qs
ps pss. dvp sp
ss s p-
s
sw p s. ts ss ss s ssp w, W
W Sz Ssp nw (WWSSn), w p-
v 100 ss zs s 1960s
1970s, s w s ssq ss ws.
t s ss s pp vss
iriS/uSgS g Ssp nw (gSn), u
ns cpsv ts b t oz (ctbto)
i m Ss (imS), u.S. dp
ds s a F t
apps c (aFtac), w v,
, pv ss ws ww. d
s s ( imS s p-
) p v v s p s s ss
p s vs. op
s s spp s
ww ssss vss,
s, v s. ts sv
s vs v p v ps ss-
, p s
ss s pss s
ss qs ss. W
ctbt s , ss w
p s s
ps vs ww.
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SeiSmological aPProacheS and reQuirementS to make ProgreSS
Develop and broadly disseminate improved 3D
wave propagation capabilities or extremely hetero-
geneous media.
Develop combined active and passive imagingmethodologies using ambient noise.
Provide dense instrumentation or 4D characteriza-
tions o near-source environments.
Explore cross-disciplinary approaches or quanti-
cation o material properties and their nonlinear
relationships.
Increase the number o inexpensive sensors andrecording systems to enable multiscale imaging o
near-surace environments over large areal extents.
Add source acilities or high-resolution shallow
subsurace mapping in diverse environments.
key QueStionS and iSSueS
How can the acute heterogeneity in the near sur-
ace best be imaged and its material properties con-
strained in diverse applications?
How do soils respond to strong ground shaking,and how are nonlinear properties o near-surace
materials best calibrated?
o what extent can seismology resolve permeability
and temporal changes in permeability at depth?
Can physics-based predictions o strong ground
motion couple with perormance-based engineer-
ing to improve seismic hazard mitigation?
How can the National Seismic Hazard Maps be
improved using advanced physics-based under-
standing o earthquake ruptures and strongground motions?
How can time-dependent properties o shallow
aquiers best be characterized to monitor water and
contaminant transport?
Can potential ground ailures rom landslides andkarst be robustly assessed and monitored?
Can nuclear testing be monitored with con-
dence levels necessary or the Comprehensive
est Ban reaty?
What is the resolution o seismological techniques
to identiy and locate unexploded ordinance, tun-
nels, buried landlls, and other human-made sub-
surace hazards?
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the crust and mantle), 3D rigidity o the lithosphere,
and identication o the brittle/ductile transition sep-
arating regions o stick-slip aulting rom ault creep.
Tese models, combined with topographic and grav-
ity data, can be used to estimate lithospheric stress and
to assess the relative contributions between internalorces and plate boundary orces.
Anisotropy is an imprinted directionality in the
structural and/or mineral abric that causes seis-
mic shear waves with dierent shaking directions to
travel with dierent speeds. Te analysis o modern
three-component digital seismograms can separate
these dierent parts o the seismic waveeld to provide
measures o anisotropy and constraints on the long-
term history o strain in the lithosphere. Anisotropy
measurements permit estimation o the magnitude
and orientation o shear strain in the ductile sublitho-
spheric mantle (the asthenosphere) and consequentinerences about the orientation o the shear stress at
the base o the lithosphere. In many cases, seismically
measured mantle anisotropy is used as a proxy or ow
or deormation. Tese studies oer unique constraints
on how ow aects plate motion and the transer o
stress to and within the lithosphere.
key QueStionS and iSSueS
What is the state o stress on active aults and how
does it vary in space and time?
What are the stress-strain laws o aults and
the surrounding crust that give rise to slow and
ast slip?
How do pore uids inuence the stress environ-
ment in ault zones?
What is the relative importance o static (elas-
tic) versus dynamic (vibrational) stress changes orearthquake triggering?
What is the time-dependent rheology (material
response to orces) and its variability throughout
the crust and mantle?
How are new aults initiated and reactivated
throughout Earth history?
Are observed statistical characteristics o earth-
quakes caused by material or geometric heterogene-
ity or by nonlinear dynamics?
Can we develop general models o strain accumula-tion and release consistent with geodesy, paleoseis-
mology, landorm evolution, and laboratory con-
straints on rheology?
SeiSmological aPProacheS and reQuirementS to make ProgreSS
Perorm rapid post-event drilling into ault zones
guided by 3D seismic imaging to quantiy rictional
heating and conduct time-dependent hydro-rac-
ture measurements to quantiy in situ stresses.
Deploy new oshore ocean bottom seismom-
eters (OBS), pressure sensors, and seaoor geo-
detic instruments to understand submarine
earthquake cycles.
Increase coordination between dierent disciplines
making stress and dierential stress measurements.
Determine changes in ault slip directions over time
and model relative to absolute stresses.
Develop robust anisotropic models or the
lithosphere.
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n Ss hz mps (p://q.ss.v/
zps/) pv ps ssss s
s ss u Ss v
s w s. t sp
s s, s s pwps - ws pss, qs s
v ss -s , s w
vs w v s ps -
. hs s q v,
v w spp w pp
zs, s pss vs
v . i s s ss p z vs
s s vs vs v
v s . avs s-
pss q p, w s-
sv p ps, w p
ps ps s. t s -
s sp ss vs-s, -s s. m v v-
qs p pps
ss, spv. V s
ss s s p s v.
t s ss ps s s
w. F p, ps s, pps
s, s s s s
s p v ss.
Ss Ps hz Ws rps S
Sid
eba
r10
Ps ss z v y m,nv, sw p (Pga) p-
s p (P.e.).
ms s s ws s w
P.e. 10% 50 s -s ss
(v sp ps) P.e.
2% 50 s. t s
pps - ws ps y
m s 1 10-8/ (P J.S. Spp i.g.
W, 2003. Ps ss z ss
y m, Ps n Ws
t rvw b, F 24, 2003.) Ps:
b s s s s
p s sv v -
ss (). t kswz-kw
n Pw P Jp (p ) ws
J 16, 2007, mw 6.6 cs
q. a s s
fs ss. t
s q s
, Jps s, s ps s.
(tp p Jps cs g v b
nws. m p t e Pw
cp W n ass P
l. b p s m. Pv.)
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detection and location algorithms. Glacial sources
that involve oating ice systems, such as calving, excite
tsunami-like ocean waves that can be detected with
seismometers deployed both on land and on oating
ice, and oer additional new opportunities or mon-
itoring key processes associated with the stability otidewater glaciers and ice shelves.
Seismic sources within the solid Earth generate waves
that propagate not only through the ground but also
through the ocean (e.g., tsunami and -phases),
atmosphere (e.g., inrasound generated by volcanic
eruptions and earthquakes), and even the ionosphere,
where remote sensing using GPS and radar technolo-
gies hold potential or new ways to characterize the
sources o large earthquakes. An explosion or distur-bance near Earths surace produces both seismic and
inrasound energy, the latter being best observed on
microbarographs or, at high requencies, by micro-
phones. Atmospheric phenomena including torna-
dos, meteorite impacts, and lightning strikes can be
monitored by collocated seismic and inrasound sen-
sors, providing new constraints on these processes
and their global occurrence. It may also be viable tocombine seismic and inrasound monitoring to detect
and quantiy wildres using similar strategies to those
used or volcanic eruptions. Seismic recordings can
also sense changes in atmospheric pressure that causes
ground tilt such as the rare Morning Glory cloud
ormations observed in Los Angeles and Australia.
Combining seismic and inrasound recordings can
help elucidate the way in which sound waves propa-
gate through the atmosphere, and thereore provide
a better understanding o atmospheric structure andits variation with time at spatial and temporal scales
inaccessible by other means.
css s vvs qv
ss psss ss
w ssp sw ssv
. F p, -q
ssp ws p s s s/s, w
s sv ss
sp. r s ps s
v ws a
s p s; s-
s s-sp
ss ws a; ss
s svs -
ss -p es s
svs s;
v v s sw -ss
s sss p
p s, s
w sv ss
sw qs j -
w s g. i
pp, ss q -
q ss
ss vv
p vs.
css
Side
bar
11
DJG
KG
HG
SG
JI
RI
NG
No.
No.
Month
Year
Glacial earthquakes in Greenland1993-2005
B) Seasonality
C) Increase over time
A) Earthquake locations
ep v ss s w ss. Ss
-p vs w gSn ss w j
s g, sw ss v. (i g. es,
m. ns V.c. ts, 2006. Ss s q g
qs, Science, 311(5768):17561758, :10.1126/s.1122112. rp w
pss aaaS.)
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and reservoir management industry. Seismologicaltechniques, including 4D (time-lapse) mapping, are
increasingly used to monitor the extraction and move-
ment o hydrocarbons and water in producing elds in
real time. Seismic exploration and production on land
and at sea is a multibillion dollar industry with major
workorce needs now and in the uture.
Resources are currently being extensively applied
worldwide to investigate geological reservoirs or their
carbon dioxide sequestration potential. Methodologies
or managing such sequestration eorts will rely crit-ically on seismology, both to monitor spatial and
temporal changes in seismic velocities correspond-
ing to the uid content, and to detect brittle-ailure-
induced microearthquakes generated by the injec-
tion process. Such methodologies are already in place
in numerous producing hydrocarbon elds to mon-
itor production and are readily adaptable to carbon
sequestration applications.
Ss f s s
e. t p s-s s
ss, v p s
s ss s-v , vp-
, , , , w
ss. is ss p 3d ss f
20 s s s-
v p, s vp 4d, -
ps p svs, sv f
s s . ts s s -
p p- q
v. t-s ss f s j -
s s, sp -
pss, s w s s ss ps-
s s. Ss s ss s
p vp, s p w;
p w s u Ss s pv v-
pp pss. cs s p
p s s sp pp
s s s. Ss s s s
- sss s s
ps, qs, v pss,
ps s ss. S p -
q s p
p p.
ep Ss rss: e m
t p s s -s ss
sv p s svs ps p
7 . t s, 3d sss ss
s p s s
p svs. ts 3d s s pps s vs s s
. us 3d ss , s s
p s s
1990. (Sp b. ds, 2005. The Leading Edge, 24:S46
S71, Ws gps. F3 ss ss
F. az, P. g, 2006, Neural Networks and Other Soft
Computing Techniques with Applications in the Oil Industry, eage b
Ss, iSbn 90-73781-50-7. Vsz J. l.)
key QueStionS and iSSueS
How can we improve the detection, characteriza-
tion, and production o hydrocarbon resources,
including detecting deep deposits beneath salt,
nding small-scale pockets in incompletely
extracted reservoirs, and monitoring porosity, per-
meability, and uid ow at high resolution?
grand challenge 5
Sidebar1
3
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changes in the mediums velocity with time as cracks
open or uids migrate through them. Seismo-acoustic
monitoring o inrasound signals rom eruptions may
be able to directly detect and recognize stratospheric
ash injection and other key eatures o eruptions at
great distances, providing rapid notication to warnaircrat o hazardous conditions.
Current eruption prediction methods are primar-
ily empirically based, because we do not have enough
inormation or a complete understanding o the
underlying physical processes. Te geometry o mag-
matic plumbing systems o volcanoes is poorly known.
o improve scientic understanding and eruption
prediction capabilities, it is essential to both improve
volcano instrumentation networks and to developadvanced methodologies that can better determine the
physical changes that accompany eruptions, including
improvements in capabilities to image the interior o
volcanic systems and to quantitatively characterize
magma migration and eruption processes.
In addition to the hazards posed by
volcanoes, volcanic processes are o
undamental interest because they
play a major role in shaping the sur-ace o the planet. Eruptions and
intrusions o magma are the pri-
mary o orming new oceanic crust.
For example, two-thirds o the Earth
is covered by basaltic oceanic crust
averaging 7-km thick, all ormed by
magma rising rom the mantle at
mid-ocean ridge spreading centers
at diverging plate boundaries during
the last 180 million years.
Hot mantle rocks partially melt and
generate magma as they rise toward
the surace at the mid-ocean ridge
because the rapid drop in pressure
in the upwelling material causes
the hot rocks to exceed the melting
temperature. In contrast, melt production beneath
volcanic arcs, such as the ring o re surrounding
the Pacic, is largely created by permeating the warm
mantle wedge with aqueous uids released rom sub-
ducted oceanic plates. Tis addition o water lowers
the melting temperature o the mantle wedge, causingpartial melting and magma ascent. Although magma
composition, as studied by geochemists and petrolo-
gists, can reveal the approximate conditions under
which melting occurred, including pressure, temper-
ature, and water content, the depth extent o melting
and the migration pathways or magma rom the deep
melt production zone up to the surace can only be
imaged with seismology.
Beneath mid-ocean ridges, mantle ow models andlow-resolution seismic tomography suggest that par-
tial melting occurs in a zone more than 100-km across
at depths as great as 100 km, yet nearly all o it emerges
at a plate boundary zone that is less than 1-km wide
at the surace. It is not known whether this ocusing
0
40
80
120
160
200
100 km 200 300 400
.08 .04 0 .04 .08
Vp/Vs
volcano
seismographearthquakes
trench
tp w P v S v s- z n. t s (s ) s
ps s s s p. t s p
s qs ps 175 . Fs s
s p w p w,
s p s s v . (i
e.m. Ss, g.a. as, k.m. Fs, l.g. mkz, c.a. r, J.m. P,
V. gzz, W. S, 2008. Ss p q -
s n cs r pp , Geochemistry, Geophysics,
Geosystems, 9, Q07S08, :10.1029/2008gc001963.)
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Understanding the large-scale patterns o mantle and
core ow both today and in Earths past is one o the
Grand Challenges conronting seismology and other
Earth science disciplines. Issues ranging rom the
thermal history o the planet to the driving orces o
present-day tectonics to how the geodynamo gener-ates the magnetic eld and why it undergoes spon-
taneous reversals are intimately linked to this topic.
Seismology has contributed greatly over the past three
decades to constraining present-day deep mantle and
core structures, and improved resolution is steadily
being achieved as data accumulate and new analysis
methods are developed. A proound result o recent
advances is the recognition that large-scale chemical
heterogeneity is present in the deep mantle and man-
tle convection is now being considered in the rame-work o thermo-chemical dynamics, as has long been
the case or core convection.
Te very large-scale 3D elastic wave velocity structure
o the deep mantle is now airly well known and is
characterized by two massive low-velocity provinces
(one under Arica and the other under the central
Pacic) surrounded by aster material. Te aster mate-
rial appears to be geographically related to present and
past subduction zones in the upper mantle, althoughcontinuity o seismically imaged ast tabular structures
throughout the lower mantle is, at best, intermittent.
Tis observation lends support to the idea o complex
mass transer between the upper and lower mantle. Te
large low-velocity structures are slow eatures or both
P-waves and S-waves, but the S-wave velocity reduc-
tions are larger than would be expected i the material
were just relatively warm. Tere are very strong lateral
gradients in velocity structure at the edges o these
low-velocity provinces, and analysis o normal modes
indicates anomalously high-density material in these
regions. Tese observations constitute strong evidence
or distinct composition or these large masses in the
deep mantle, and deep mantle convection must involve
both thermal and chemical variations.
grand challenge 9.
hoW do temPerature andcomPoSition VariationS control
mantle and core conVection?
g 3d ( pp s
- ) ss v s -
s ss p. r s v v w
S-wv vs, w s v v s S-wv v-
s. t s w s w-v s,
a P ps,
vs s zs P.
(i s a. dzws).
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rom a combination o limitations in global sampling
by seismic waves due to lack o seismic stations in the
ocean and in the southern hemisphere, and o limita-
tions o seismic imaging theory and applications that
are currently being used. Enhanced data collection and
imaging o velocity structure at every scale is essential,but there is also the need to improve global anisot-
ropy and attenuation models, which enhance our abil-
ity to connect seismological observations to mineral
physics and geodynamics.
Seismology constrains the average structure o the
metallic uid outer core and solid inner core to high
precision, but it cannot resolve the convective ow eld
in the outer coregeomagnetic studies are the only
current approach to doing so. o rst order, there does
not appear to be detectable seismic velocity heteroge-neity in the outer core, consistent with it being a very
low-viscosity uid, but there are indications o inho-
mogeneous in structure in both the uppermost and
Ss vs es s sps p.a s ( sz es ),
ps p : s pssv z s -
ps ps ps
q , w svs s s
v s es . i
ps w s, ss ss v v vs
s pps ,
s vs sp.
t s , s v sp s-
, s wvs v s
p p w p q p. b, -
s s s-
p, s s s sp. l-s s
ps ; ss vs ,
ss wvs s -
sp ws sp. t s s -s
(w ) w . a s
p s p, s pp ps-
s -pss pss
sz ss.
i s p s
s v .
t ws svs ss-
s v P-wvs s
v sv s ( s -
p -q ss svs). t v
s v s, vv s s -
s p vs s p. tv
s v s sv fs
s, p s s.
t s qs v
w s
vs f fw v
s s .
cs s s s
vs v w
s. c ss, p,
ss s s w
, w s s p s s.
ts pss w s v
, s p, .
t mss i c
Sidebar
20
t-s s sp w
p . t s s w
P-wvs v ss, w -
s w s sw vs p. t s
s w sp. t s pzz w
s ws sps . t
( ) s s sp s
s. (i s x. S.)
180
0
270 90
NPNP
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Ss p v
s psss
sps, s, s-
s s ss, ss sss
p v. a v ss
m ap p v
q
ms s, -
ss s , ps
w-v z p 400 ,
v w ss v
v s qs fs s,
pss s p -
s . dps ss-
s p s p
ss s s qss,
s s s s p
q s, w p-
s w s ms,
ss s-w
ep, s -
Vs. a v p
pss s ss-
pps, ss-
s pv p -
.
a sss m w pv pp-
s p s s qss, : ds
ms s spp - j p e? W s
- w m, w s s
w p qs? W s ps -
s s w qs
ssss es v ? a -
ss p qs s ss
sps p qs e? a s vs
s ps s s s? hw
s ps s, s -
s 3d p?
a s ps ss p-
sss ms, s s-
, , p sss p ps, ws, s , v-
. ms s v
psss, pp s sp w s
s ss w ss q z-
s s sp ws. k
ps ss
s p, s -
w/ s, s v-s ss w ps s
p p. d q ps
w s v s s s s.
Vs m ps v -
s, ss s v
w . S p s ep,
g, es s s ss-
s ps
fs. ass v pps,
s ss ps s p-
pps s s -p . gv
p v ss s, v
ss s s ss s -s p ss s
.
P Ss
Sidebar
21
bzz a p ss
m ap 11 ss.
(i s naSa.)
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55
Internal boundaries in the Earth are associated with
the primary compositional layering that resulted rom
chemical dierentiation o the planet (the crust, man-
tle, and core) and with mineralogical phase changes
controlled by pressure and temperature variations (the
transition zone and deep mantle velocity discontinui-
ties and the inner core boundary). Tese variations can
produce signicant accompanying changes in compo-
sition and rheology. Tese boundaries can thus exert a
strong inuence on mantle and core convection, par-
ticularly i they serve as thermal boundary layers, and
their seismically determined properties can constrain
internal composition and temperature when calibra-
tions rom mineral physics are available. Seismology
can characterize the depth (pres-sure) and elasticity contrasts
across internal boundaries with
high precision. Te rontier o
research now lies in mapping
the 3D topography and sharp-
ness o Earths internal boundar-
ies, which are key to quantiying
their mineralogical and compo-
sitional nature. Te seismological
methods that are needed involvewaveorm modeling and wave-
eld migrations, complementing
travel-time tomography, which
is better or resolving volumetric
heterogeneities. Detailed imaging
and interpretation o the ther-
mal, compositional, and dynam-
ical processes near Earths inter-
nal boundaries are the principal
components o one o the Grand
Challenges or Seismology.
Radial models o the mantle
include globally extensive seis-
mic velocity jumps near depths
o 410, 520, and 660 km, which
are generally attributed to phase
grand challenge 10.
hoW are earthS internal boundarieSaFFected by dynamicS?
S pp S a (p) vs v-
pp es pp ps s ss
410 () 660 () p. tpp ss s
s z ps w e.
i s , psss s psss, w
P p sp ss S a.
(i s n. S.)
grand challenge 10
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changes in major upper mantle minerals such as oliv-
ine. Laboratory and theoretical calibration o the
pressure-temperature-composition behavior o man-
tle minerals allow seismic observations to be inter-
preted in terms o absolute temperatures and compo-
sitional models. Tis allows high-resolution imagingo lateral variations in depth o the discontinuities to
provide direct constraints on ow across the phase
transition boundaries. omographic images o sub-
ducting oceanic lithosphere have established that slabs
either deect and accumulate in the transition zone or
penetrate directly into the lower mantle, so it is clear
that transition zone boundaries can prooundly aect
mantle convection. Many other upper mantle seismic
reectors have been detected over localized regions,
notably under cratons and beneath back-arc basins.Understanding the cause o this seismic velocity
reectivity and how it is aected by dynamics o the
mantle wedge may undamentally change our notions
o the creation and stabilization o continental litho-
sphere and how it has changed through time.
Seismic reectors in the deep mantle have also been
detected, both in 3D scattering images o near-verticalmid-mantle heterogeneities that are plausibly eatures
produced by ancient subducted slabs, and in reec-
tions rom the sharp edges o the large low-velocity
provinces under the Pacic and Arica. Tere is also
a globally intermittent reector o seismic waves
ound 200300 km above the core-mantle bound-
ary. Tis boundary is now widely attributed to the
recently discovered mineralogical phase transition
rom the most abundant mineral in the lower man-
tle (magnesium-silicate perovskite) to a high-pressure(post-perovskite) polymorph. Seismic waves also
reveal the presence o an extensive, but intermittent,
100km
200km
300km
400km
500km
600km
0km
TongaTrench
css ss 3d
ss
S-wv fv w
j s t s. Qs-
z ss s w
s pp p s.
(i s y. Z.)
grand challengeS For SeiSmology
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57
very thin (< 30 km) ultra-low veloc-
ity zone located just above the core-
mantle boundary. Tis low-velocity
zone is commonly attributed to par-
tial melt being present in the hottest
part o the thermal boundary layer,although strong chemical contrasts
may also be involved. All o these
seismological structures have impli-
cations or deep mantle dynamics.
Analysis o boundary layer pro-
cesses provides internal tempera-
ture probes along with constraints
on rheology and composition.
Improved seismological constraintsplay a unique role in discovering and
understanding these boundaries.
400 km
CMB100 km
X2
X1L2
L2
L1
L1L1
310km0
phase transition height above CMB [21]
m S-wv f s - (2) p f-
250 v - (1). (i r.d. v hs, m.V.
hp, P. W, S.-h. S, P. m, l. t, 2007. Sssp
s es - , Science, 315:18131817, :10.1126/
s.1137867. rp w pss aaaS.)
key QueStionS and iSSueS
How sharp are internal mantle and core boundaries?
What is the multiscale topographic structure and
lateral extent o mantle boundaries, including the
core-mantle boundary?
What are the eects o the transition zone bound-
aries on mass ux between the upper and lower
mantle?
Are there thermal boundary layers that serve as
sources o mantle plumes at any o the internal
boundaries?
Is post-perovskite present in the mantle and does it
exist in lenses or as a layer?
What is the cause o the ultra-low velocity zone at
the base o the mantle, and how has it evolved?
How can seismological observations constrain heat
ux across the boundaries?
o what degree are variations in water content and
chemical heterogeneity responsible or topography
on mantle discontinuities?
Can we detect time-dependent changes in bound-
ary properties?
Are there stable thermo-chemical boundary layers
in the outermost outer and lowermost outer core?
What causes hemispherical variations just below
the inner core boundary and what is the source o
deeper anisotropy?
grand challenge 10
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enhancing acceSS to high-PerFormance comPuting caPabilitieS
building and SuStaining the ProFeSSional PiPeline
Increasingly massive seismic data sets, very large inver-
sions or 3D and 4D multiscale models o Earths inte-
rior, and robust orward calculations o broadband seis-
mic ground motions or realistic, nonlinear eects o
earthquake and explosion sources as well as 3D struc-
ture present enormous computational challenges that
exceed the capabilities o the most advanced comput-
ers presently available. Advancing seismology research
at universities and elsewhere will rely on access to
resources ranging rom moderate-size, in-house com-
puter workstations and clusters to large-scale computa-
tional capabilities, such as those at national laboratories
in tandem with integrated cyberinrastructure net-
works such as eraGrid. Access to high-perormance
Key to all undertakings in seismology is maintaining
and supporting a steady pipeline o talented people
with solid quantitative skills into university programs
that provide undergraduate and graduate training inundamentals and applications o seismological theory
and prepare new seismologists or tomorrows chal-
lenges. Retention o this talent and expertise in indus-
try, national laboratory, academic, regulatory, state, and
ederal agency careers requires continued collaboration
among academia, unding agencies, and employers to
establish sustained supporting structures. Te seismol-
ogy workorce demands o industry are not presently
being ully met and new and stronger partnerships
between relevant industries (e.g., energy, insurance,engineering) and academic programs should be devel-
oped to attract undergraduates and graduate students
to the discipline.
Attracting top students to this exciting and important
discipline requires improved outreach that highlights
its many societal contributions and exciting research
computing, coupled with urther improvements in the
standardization and dissemination o advanced seis-
mic sotware (such as is currently being pursued by the
NSF Computational Inrastructure or Geodynamics
[CIG] initiative), is essential to advancing the disci-
pline, both in acilitating new methodological break-
throughs and in providing access to state-o-the-art
capabilities to more institutions.
RECOMMENDATIONS
Make available to the broad research community
careully vetted seismological sotware and pro-
cessing tools, along with integrative data products.
Tere is also a special need in developing coun-
rontiers. Broadly based eorts to enhance public
awareness o the importance o the discipline, as con-
ducted by Education and Outreach (E&O) eorts o
IRIS, SCEC, and EarthScope as well as many uni-versity programs, are highly benecial long-term
investments that play a critical role in showcasing the
importance o seismology and its numerous contribu-
tions to society.
RECOMMENDATIONS
Further engage seismology community organiza-
tions with industry to increase awareness o oppor-
tunities in seismology among undergraduates and
high school students. Expand E&O eorts o these organizations to pro-
mulgate public awareness o the discipline and its
societal contributions, and support undergraduate
and graduate training materials and enhanced edu-
cational opportunities.
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scientic advances, to broaden the pool o academic
groups conducting such work, to advance partnership
opportunities with industry, and to enhance core edu-
cational opportunities or Earth science students.
Te vibrator trucks o the Network or EarthquakeEngineering Simulation (NEES) acility could be
made more available or seismological research on
very shallow structure, which may require increased
exibility in the current operation o this acility.
NEES vibrators lack sufcient capabilities or crustal-
scale imaging. Te controlled-source seismic imag-
ing eorts o the USGS have substantially diminished
over the past several decades, and there is no longer a
dedicated internal program to collaborate with uni-
versities in the permitting and handling o buriedexplosive sources, which requires highly specialized
expertise and is acilitated by government participa-
tion. Drilling shot holes or explosives and vibrator
truck arrays can both be subcontracted commercially,
but the substantial cost is a signicant impediment to
most researchers and current research program bud-
gets. Establishing a broad-based community source
acility, including drill rigs, explosive-handling capabil-
ity, and a vibrator array, and integrating the needs and
resources o IRIS, USGS, and NEES, would sustain
the health o active seismic imaging at all scales. Tis
acility could work on a model similar to DOSECC,
which provides scientic drilling rigs, combined withexpertise or the contract hiring o industry rigs where
appropriate and cost eective.
RECOMMENDATIONS
Establish a acility or collection o acilities or
sources used in active-source seismology so that
research programs and education in this area can be
sustained. Tis acility could possibly be developed
through access to the vibrator trucks o NEES,
reinvigorated participation o the USGS in active-source seismology, and in partnership with industry.
Improve interactions among academic, governmen-
tal, and industrial eorts in active-source seismol-
ogy to sustain the discipline.
Expand the ability to conduct 3D active-source
imaging at sea.
Producing adVanced SeiS mological data ProductS
Te diverse applications o seismology or basic
research and environmental monitoring all benet
rom the long-standing eorts to produce catalogs o
earthquake parameters (location, origin time, mag-
nitude) and mathematical representations o Earth
structure (1D, 2D, and 3D seismic velocity and den-
sity distributions). Seismic source catalogs and mod-
els are used widely beyond seismology, extending the
disciplinary impact to earthquake engineering, earth-
quake insurance, geotechnical, geological, and geo-
chemical arenas. Indeed, the principal seismic data
or most o these communities are earthquake cata-
logs rather than seismograms. It is incumbent upon
the discipline to provide the most reliable and com-
prehensive compilations o seismological knowledge
to all users. However, the distributed nature o the
many eorts that produce earthquake parameter lists
and Earth models on various scales leads to an array
o products that lack clear authoritative validation and
easy access. Te widespread use o the 1D Preliminary
Reerence Earth Model (PREM), produced in 1981,
clearly demonstrates the importance o well-dened
syntheses o seismological knowledge.
Recent advances in data quality and availability,
advanced processing methods, and computational
capabilities enable signicant improvements in earth-
quake catalogs and Earth models, yet there is not a
dedicated eort to systematically enhance these unda-
mental seismological products. It is realistic to commit
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enhancing Free an d oPen acceSS to data
Seismology is an intrinsically global and interna-
tional undertaking, and it relies upon strong coordi-
nation and cooperation among governments, interna-
tional organizations, and universities. Seismological
contributions are greatly served by global open access
to real-time seismic data rom all international data-
collection activities, building on the examples o the
USGS NEIC, IRIS DMC, and FDSN-participant
data centers, along with many U.S. university pro-
grams. Eorts to provide access to data that are not
now reely available, such as the IMS seismic record-
ings, thousands o instruments in national regional
recording systems, and other currently restricted
seismic data sets, will enhance multi-use o the cor-
responding signals or investigating important top-
ics in the Earth system. Global concerns about earth-
quake hazards, environmental change, and nuclear
testing present many opportunities or international
partnerships and interactions on technology transer,
capacity-building, condence-building, and integra-
tive hazard assessment that are all complemented by
basic research. Te advanced state-o-the-art o seis-
mology in the developed world can be leveraged to
enranchise and bolster progress in developing nations
that are struggling to deal with challenging hazard
issues and limited resources.
to monitoring almost all seismicity on all continents
down to magnitude ~ 3 events, and beneath the oceans
down to magnitude ~ 4, over the next decade. Event
location accuracy can be systematically improved on
large and even global scales, with relative locations as
accurate as a ew hundred meters rather than currentlevels o a ew to tens o kilometers. Integration o cat-
alogs rom various seismic systems into an authorita-
tive, readily accessible global seismic source database
would benet basic research, applied research, and
many societal applications that use seismicity distri-
butions. It is also realistic to commit to developing a
consensus 3D Earth model as a reerence structure
or diverse applications. Tis is a very complex under-
taking and should be coordinated at the agency level,
with an understanding that models evolve and requireupdating as data and methods improve.
Natural disasters provide both learning and teaching
opportunities that can be exploited i inrastructure
is in place in advance. Rapid responses to exploit the
window o opportunity or making critical transient
observations (e.g., ault-zone drilling, hydrological
monitoring, atershock recording, volcanic deorma-
tions) must be planned in advance. Rapid dissemina-
tion o seismological inormation to educators, emer-
gency response coordinators and the general public
also requires in-place inrastructure.
RECOMMENDATIONS
Integrate regional and global seismic bulletins intoan openly available, denitive international seismic
source catalog.
Commit to improving earthquake location accu-
racies on large scales by using advanced process-
ing methods and strive to complete catalogs down
to levels o magnitude 3 in continents and 4 in
oceanic regions.
Develop a 3D Earth model as the next generation
community model beyond PREM, describing the
anelastic, anisotropic, aspherical Earth structure bystandardized parameterization that can be used by
multiple disciplines.
Provide ready access to products o seismologi-
cal research in orms that are useul to ellow Earth
scientists to acilitate dissemination o seismologi-
cal knowledge.
Expand inrastructure or learning rom disas-
ters and mounting scientic response, along with
improved outreach with inormation or the public.
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enhanced interdiSciPlinary coordination
Progress on the Seismological Grand Challenges listed
in this long-range plan and the many societal appli-
cations o seismology hinges on improved interdisci-
plinary interactions and communications. Strong syn-
ergisms exist within the Earth science arena between
seismology and other disciplines, such as geodesy, geo-dynamics, mineral physics, geology, and geochemistry.
Tese connections are ostered by proessional societies
such as the American Geophysical Union (AGU), the
Society o Exploration Geophysicists (SEG), and the
International Association or Seismology and Physics
o Earths Interior (IASPEI). Research coordination
is abetted by NSF-unded community organizations
and consortia such as IRIS, the Southern Caliornia
Earthquake Center (SCEC), the Cooperative Institute
or Deep Earth Research (CIDER), the Consortiumor Materials Properties Research in Earth Sciences
(COMPRES), and the geodetic consortium
UNAVCO. NSF programs such as EarthScope,
MARGINS, RIDGE, and CSEDI also enhance mul-
tidisciplinary communications. Coordination with the
National Ecological Observatory Network (NEON)
can augment societal applications o seismology. Te
United States has only limited ties between industry
and academia or workorce training and technology
development in active-source seismology. Many o the
novel seismological areas o research identied in this
document, including some aspects o atmospheric, cli-
mate, and ocean research, are at early stages in build-
ing constructive coordination among science commu-nities, unding agencies, and industry.
RECOMMENDATIONS
Sustain multidisciplinary integration eorts and
oster improved communications and coordina-
tion on seismology activities among NSF divi-
sions o Earth Sciences, Ocean Sciences, and
Atmospheric Sciences, and the Ofce o Polar
Programs. Overcome existing institutional barri-
ers to optimal cross-divisional seismology activitiesthrough coordination at the Geoscience Directorate
level o NSF.
Encourage ederal and state agencies, universi-
ties, and scientic organizations to support inter-
disciplinary workshops on critical interaces in the
shallow Earth system, extreme environments, deep
Earth processes, and environmental change with
active participation by seismologists.
RECOMMENDATIONS
Continue to have ederal programs and seismology
organizations strongly advocate or open access to
seismic data on a global basis, with real-time access
to the greatest extent possible.
Communicate and oster seismological capabilities
or addressing hazards and environmental moni-
toring concerns and data exchange with developing
nations through coordinated international eorts.
SuStaining a healthy Future For SeiSmology
adVanceS in inStrumentation
echnological advances permeate the discipline o
seismology, which has been a scientic leader in
embracing advances in computer storage, digital pro-
cessing, telecommunications, Internet dissemination
o inormation, and other technologies. Specic to
the discipline are needs or urther advances in seis-
mic sensors and high-resolution data acquisition. Te
current sensors or recording very broadband (VBB)
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seismic data at the long-period end o seismic ground
motions (Streckeisen SS-1 sensors deployed in many
seismic networks) are no longer being produced and
will need replacement as they age. Development o a
next-generation VBB sensor is a high priority, and is
required to ensure on-scale, complete recordings othe very largest earthquakes, such as the 2004 Sumatra
tsunami earthquake, and to record with high delity
Earths ree oscillations, slow earthquake motions, and
very-long-period noise arising rom oceanic, atmo-
spheric, and other sources. New micro-electro mechan-
ical systems (MEMS) are being designed to sense
short-period ground vibrations, and urther develop-
ment o this technology may soon enable vast increases
in numbers o inexpensive sensors that can provide
high-density sampling o ground motions in urban andremote areas. Extension o the usable period band or
MEMS or other novel low-cost sensors to the range
o tens o seconds would usher in a revolution in seis-
mic tomography o the deep Earth by acilitating 3D
and 4D crust and mantle imaging experiments using
orders o magnitude more receivers than are eldable
with current (e.g., IRIS PASSCAL) seismometer tech-
nology. New seismic sensors or hostile environments
(extreme cold, ocean bottom, deep boreholes, and
extraterrestrial environments) are critical or expand-ing the scientic reach o seismology and or address-
ing the disciplines Grand Challenges. University par-
ticipation in seismic instrumentation development
has diminished over time, and sustaining specialized
expertise in ground-motion measurement technolo-
gies is a challenge that conronts the discipline.
RECOMMENDATIONS
Encourage collaborations across ederal agencies
that utilize very broadband seismic data or moni-
toring purposes to support development o next-
generation very broadband seismometers to replace
current instruments. Explore MEMS technologies to develop low-
cost seismic sensors that can be deployed in great
numbers and can supplement or replace current
seismometers.
Increase the number o strong motion instruments
near aults and in urban areas to improve con-
straints on rupture processes and to better under-
stand the relationship between ground motion and
building damage.
Continue to develop next-generation telemeteredseismic instrumentation in hostile environments
(e.g., volcanoes, glaciers, seaoor).
Develop partnerships among industry, national lab-
oratories, academia, and ederal agencies to advance
and sustain seismic instrumentation innovation
and capabilities.
Sustain existing permanent networks, such as
the GSN and ANSS, as long-term observa-
tional systems or both research and monitoring,
through stable unding rom multi-agency part-ners and continued upgrades to improve reliability
and efciency.
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eismology is an exciting, vigorous, and important discipline, with broad relevance
to major challenges conronting society, including environmental change, cop-
ing with natural hazards, energy resource development, and national security.
Seismology provides the highest-resolution probes o inaccessible regions o Earths
interior rom shallow crustal sediments to the central core, and thus plays a primaryrole in eorts to understand the structure and dynamics o Earths many internal sys-
tems. Te discipline has grown to its current prominence by sustained ederal support
o basic research, which ensures training o new generations o seismologists via uni-
versity research programs, along with technical developments that enhance applied
research in nuclear monitoring, exploration and resource management seismology,
earthquake and volcano hazard monitoring, and environmental change evaluation.
Looking to the next 10 to 20 years, the seismological community has herein dened
10 Grand Challenge basic research questions where seismology oers the opportu-
nity or undamental contributions. Tese topics all address Earth systems that can beprobed and quantied using seismological techniques. Tis document identies scien-
tic challenges and opportunities or basic research in seismology to be supported by
ederal, university, state, and industry programs. It is hoped that this document will use-
ully inorm and inspire program managers and agency directors to help advance and
sustain the critical in rastructure, workorce, and scientic capabilities necessary or the
eld to ully realize its potential contributions to science and to society at large.
S
Summary
Summary
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eismological approaches to solving the Grand Challenges described in this
document include a plethora o analysis techniques and distinct seismic wave
analyses. Underlying all o the methods are some intrinsic attributes o the
discipline that warrant discussion. Tese include the practices o monitoring Earths
natural and human-made sources, and the practices o imaging Earths systems and
modeling the ground shaking using the resulting Earth models.
S
aPPendixkey SeiSmological PracticeS
monitoring dynamic ProceSSeS
in earthS enVironment
Earthquakes, volcanoes, ocean storms, glacial ows,and many other natural sources are located, identi-
ed, and quantied through undamental monitor-
ing practices o seismology. Tese practices require
long-term operation o many seismometers in arrays
and networks o various scales with continuous data
telemetry. Monitoring operations include sparse
global seismographic networks with very broadband
recording capabilities, dense regional networks with
high-resolution capabilities, and temporary deploy-
ments in remote ar
