U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

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1906

National Geograp hic, Esri, DeLorm e, HERE, UNEP-W CM C, USGS, NASA, ESA, M ETI, NRCAN, GEBCO, NOAA, increm ent P Corp .

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UnitedStates

Mexico

PacificOcean

44120°

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40° 40°

M6.0 South Napa, California Earthquake of 24 August 2014

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Mexico

Montana

IdahoOregon

California

Nevada Utah

Arizona

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0 500 1,000 1,500250Kilom eters

Prepared in cooperation with the Global Seismographic Network

Tectonic Setting

Seismic Hazard

Epicentral Region

EXPLANATIONMain Shock

_̂Earthquake Magnitude( 5.5 - 5.99

( 6.0 - 6.99

( 7.0 - 7.99

( ≥ 8.0

Earthquake Depth (km)!( 0 - 69

!( 70 - 299

!( ≥ 300Aftershocks

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Faults

EXPLANATIONMain Shock

_̂Mag >= 7.0!( 0 - 69 km!( 70 - 299!( 300 - 600Plate Bound ary# Sub d uc tion

TransformDivergentOthers

V olcanoes#*

0 500 1,000 1,500250Kilom eters

Epicentral Region

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Epicentral Region

DATA SOURCESEARTHQUAKES AND SEISMIC HAZARD USGS, National Earthquake Information Center NOAA, National Geophysical Data Center IASPEI, Centennial Catalog (1900 - 1999) and extensions (Engdahl and Villaseñor, 2002)EHB catalog (Engdahl et al., 1998)HDF (unpublished earthquake catalog, Engdahl, 2003)Global Seismic Hazard Assessment ProgramPLATE TECTONICS AND FAULT MODELPB2002 (Bird, 2003)Hayes, G. P., Wald, D. J., and Johnson R. L., 2012, Athree-dimensional model of global. subduction zonegeometries: Journal of Geophysical Research, v. 117,B01302, . doi:10.1029/2011JB008524.DeMets, C., Gordon, R.G., Argus, D.F., 2010.Geologically current plate motions, Geophys. J. Int. 181, 1-80.BASE MAPNIMA and ESRI, Digital Chart of the WorldUSGS, EROS Data CenterNOAA GEBCO and GLOBE Elevation Models

DISCLAIMER

Base map data, such as place names and political boundaries, are the best available but may not be current or may contain inaccuracies and therefore should not be regarded as having official signifiance.Map updated by U.S. Geological Survey National Earthquake Information Center26 August 2014http://earthquake.usgs.gov/Map not approved for release by Director USGS

REFERENCESBird, P., 2003, An updated digital model of plate boundaries: Geochem. Geophys. Geosyst., v. 4, no. 3, pp. 1027-80.

Engdahl, E.R., and Villasenor, A., 2002, Global Seismicity: 1900-1999, chap. 41 of Lee, W.H.K., and others, eds., International Earthquake and Engineering Seismology, Part A: New York, N.Y.,Elsevier Academic Press, 932 p.Engdahl, E.R., Van der Hilst, R.D., and Buland, R.P.,1998, Global teleseismic earthquake relocation with improved travel times and procedures for depth determination;Bull. Seism. Soc. Amer., v. 88, p. 722-743.

M6.0 South Napa, California Earthquake of 24 August 2014 24 August 2014 10:20:44 UTC 38.22° N., 122.313° W.Depth 11.3 kmMw = 6 (USGS)

EARTHQUAKE SUMMARY MAP

PAGER

PACIFIC PLATE

ShakeMap

TECTONIC SUM M ARYThe earthq uake lies within a 70-km -wid e (44 m iles) set of m ajor faults of the San And reas Fault system that form s the b ound ary b etweenthe Pacific and North Am erican tec tonic p lates. The p ersistent northwestward m ovem ent of the Pacific p late relative to North Am ericap rim arily causes right-lateral slip ac ross the m ajor faults, b ut also causes d eform ation b etween the m ajor faults. The ongoing c om p lexd eform ation field is revealed b y m od ern geod etic surveys and earthq uake p atterns as well as the regional geologic struc ture. Theearthq uake is located north of San Pab lo Bay b etween two m ajor active fault system s: the Hayward -Rod gers Creek Fault system on thewest and the Conc ord -Green V alley Fault system on the east. The earthq uake oc curred near the well-known W est Nap a Fault, and the lesswell known Carneros-Franklin Faults, whic h juxtap ose d ifferent suites of roc ks. Although there are several faults in the region of theearthq uake, only the W est Nap a Fault is known to have d isp laced Holocene-age sed im ent — whic h is p ositive evid ence of surface faultrup ture in the last 11,000 years.Historically, in this region shaking suffic ient to seriously d am age structures at M are Island oc curred d uring the M 6.8 1868 Hayward Faultearthq uake, the M 7.8 1906 San And reas Fault earthq uake, and p articularly d uring the M 6.3 1898 M are Island earthq uake. The 1898earthq uake m ay have oc curred ab out 20 km (12 m iles) to the northwest on the southern Rod gers Creek Fault. Even larger nearb y eventsthan the 1898 earthq uake can b e exp ec ted in the future. In ad d ition, the ep icentral region of this earthq uake is d ep ic ted on the USGSNational Seism ic Hazard M ap s to have a high p rob ab ility of strong shaking in the future.The Hayward -Rod gers Creek Fault system , whic h is ap p roxim ately 11 km (7 m iles) west of the ep icenter, generated d am agingearthq uakes in 1868 and p rob ab ly in 1898. The Conc ord -Green V alley Fault system , whic h is 14 km (9 m iles) east of the ep icenter,p rod uced a M 5.5 earthq uake in 1954; while it has not generated a large historical event, there is strong evid ence for recent p re-historicac tivity. The 1999 W orking Group on California Earthq uake Prob ab ilities (W G99, 1999) conc lud ed that the Hayward -Rod gers Creek Faultsystem has a 32 p ercent p rob ab ility of generating a large earthq uake (M 6.7 to 7.4) b y the year 2030, and the Conc ord -Green V alley Faultsystem has a 6 p ercent c hance of generating a large earthq uake (M ≥6.7) in the sam e tim e p eriod .The b ayshore areas in the San Franc isc o Bay region are und erlain b y land fill and b ay m ud and have exp erienced d isp rop ortionatelygreater d am age d uring historic earthq uakes. Such d am age is caused b y soil failure in the fills and am p lification of ground shaking b y thesoft b ay m ud .

NORTH AMERICA PLATE

Explanation2014 Seismic Hazard2% in 50 Year PGA (g)

0 - 0.020.02 - 0.040.04 - 0.060.06 - 0.10.1 - 0.140.14 - 0.20.2 - 0.30.3 - 0.40.4 - 0.8> 0.8

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