Application of GPS to Giant Earthquake

Cases study: 2010 Maule Chile Earthquake Mw8.5

2011 Tohokui Oki, Jaban Earthquake Mw 7.8

Presented by

Ashraf Mohamed Rateb

ID:P68017014

Ph.D. student, Geodetic Science lab

arateb@narss.sci.eg

• Agenda

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How does GPS work?& Processing stratgey

1. Problem statement

2. Cases study

A. Maule Earthquake 2010 Mw 8.6

A.1. Objectives

A.2.Data

A.3.Processing Steps

A.4. Results and Discussions

A.5.Concluions

B.Tohoki Oki Earthquake 2011 Mw 7.8

B.1. Objectives

B.2. Data

B.3. Results and Discussions

B.4.Concluions

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How does GPS work?& Processing strategy

Figure 6 show scheme processing of GPS data.

GPS Observation Analysis simulates a real real-time situation

only use information that can be available in real time

– 24 hours of 30 30-sec data up until 20 minutes after origin

time

Estimated Parameters

• GPS satellite and station clocks (= double differencing)

• Station positions

• Earth's pole position and rate of rotation

• Tropospheric zenith delay and gradients (random walk)

• Multipath mitigated using position-based sidereal filter

Various Orbit Strategies Compared

– Broadcast / IGS Ultra Rapid Orbits / Custom Estimation

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Tokai Region, Central Japan4

Results ~ Earthquakes

Using estimated orbits• Rapid displacement

• Data confirm that it arrives mostly with body waves

• Can be used to estimateearthquake slip modelModel displacements ~ 3 mm

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• Problem Statment

http://earthquake.usgs.gov/earthquakes/world/world_deaths.php.,, USGS.

Figure 2 Human lives lost to earthquakes yearly since 1990.

Crustal deformation is a direct manifestation of the processes that result in earthquakes (Dixon., 1995).

Keelung,Taiwan

Landslide Near Taipei

Japan Tsunami 2011

Spatial distribution of earthquakes along plate boundaries

Figure 3 disasters of earthquake

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Magnitude 9.0

Date-Time

March 11, 2011 •at 05:46:24 UTC

Location 38.297°N, 142.372°E

Depth 30 km

MAGNITUDE 8.8

Date-Time

Feb 27, 2010at 06:34:14

Location 35.909°S,72.733°W

Depth 35 km

Figure 4. Locations of Maule 2010 and Tohoki Oki earthquake 2011

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A.2.Objectives

Inferring the static deformation and the kinematics of the 2010 moment magnitude (Mw) 8.8 Maule mega thrust earthquake.

Why the Maule earthquakes became amegathrust earthquake?

Relocation of epicenter of (Mw) 8.8 Maule mega thrust earthquake.

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A.2.Data• Seismic gap (Concepción-Constitución seismic gap in central Chile.

Gap had been defined from the size of the 1835 Mw8.5 earthquake.

• GPS Data

2000-2010 (Before and After event).

20 continuous Global Positioning System (cGPS) stations in the region

between37°S and 28°S.

Far-field cGPS stations more than 3000 km away from the epicenter,

in Brazil, French Guyana, South Patagonia, and Galapagos, (a fixed

reference frame together with several stations on the Brazil-

Aregentina)

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Figure ( 5 ), distribution of Andes GPS Array station map (http://www.tectonics.caltech.edu/_ )

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Fig. 7. Coseismic static displacement field derived from cGPS sites. Bold numbers s give the displacement in illimeters, except for the >1-m displacements Stars depict hypocenter locations: NEIC (white), SSN (black), this study (red).

Small yellow dots plot the locations of 1 month of aftershocks (NEIC). Color stripes along the trench depict past earthquake rupture zones (6–12). ETOPO-5and GTOPO-30 Digital Elevation Models were used to generate the background topography and bathymetry Color-coded curves next to displacement arrows at selected sites (left column).

Results and discussion

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Fig. 7A.Coseismic static displacement field for survey sites (red arrows)and cGPS sites

(green arrows) in the epicentral area horizontal component

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Fig 7. (B). vertical component.Bold numbers next to arrowheadsgive the displacement in centimeters.Ellipses depict the 99% confidencelevel of formal uncertainties.

Blue lines mark zones withsubsidence larger than ~50 cm,yellow lines similarly show values ofuplift. mark zones where verticalmovement is difficult to evaluatebecause it is close to zero severaltens of , _+m);

Dashed lines indicate where data arescarce or lacking.

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Fig. 8.Coseismic and afterslip source models.

Red colors show the extent and the amount of coseismic slip (scale from 0 to 20 m). Dark red arrows depict the amount and direction of slip on the fault plane.

Blue contour lines show the 12-day post-seismic afterslip (contour level every 10 cm).

Dots show locations and data type used in the inversion (black dots for GPS data: Small for survey markers and large for cGPS stations;

pen dots for land-level data from natural or anthropogenic marker). Stars show hypocenter locations: NEIC (white), SSN (black), this study (red). The twodashed lines depict the profiles of fig. S1

Conclusions

A total rupture length of ~500 kilometers where slip (up to 15 meters)

concentrated on two main asperities situated on both sides of the epicenter.

The rupture reached shallow depths, probably extending up to the trench.

The low-frequency hypocenter is relocated 40 kilometers southwest of initial

estimates.

Rupture propagated bilaterally at about 3.1 kilometers per second,

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Case study II

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Figure 10: Location map of the 11 March 2011 Mw 9.1 Tohoku-oki earthquake. ) Red star indicates the epicentre position1. Red and white “beach ball” represents the focal mechanism of this earthquakeRed triangles indicate the DART stations used in the inversion; b) Yellow, pink and cyan shadow zones are approximated rupture areas of the 869 Jogan, 1896 and 1933 Sanriku-oki earthquakes respectively. Cyan circles indicate GPS stations onshore, magenta circles the geodetic seafloor observation sites15 red triangles the bottom pressure sensors and GPS-buoys ,White arrow indicates the approximate convergence direction of the Pacific plate (estimated velocity of 9.2 cm/yr).

Magnitude 9.0

Date-Time

March 11, 2011 •at 05:46:24 UTC

Location 38.297°N, 142.372°E

Depth 30 km

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Figure (11), distribution of Jaban GPS Array station map (http://www.tectonics.caltech.edu/_ )

DataGPS Data(USA array +GSI Array)+Tsunami Data

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Fig 12 Map of the central and northern honshu japan vectors Indicated the

• horizontal components of the gps displacements for the main shock (yellow) And the mw 7.9 aftershocks (orange).

• yellow and orange moment tensors indicate the w-phased centorid for the main shock and the gcmt t(global moment centroid ) location of the 7.9 after shock. The closed yellow curve indicates the outline of the mw9.0 main shock (8m slip contour).

• The white arrow indicated the direction of convergence between the pacific plate and northern japan . t,s, and k indicate the cities of tokyo, sndai , and kamaishi.

• The yellow box in the inset reference map shows the region of this figure rand locations of deep sea bottom pressure gauge used in this study, all superimposed On the peak tsunami Wave heights redicated by our preferred earthquake source model.

Results & discussions

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Fig.14.Inferred distribution of subsurface slip distribution (color and black contours with a contour interval of 8 m ). Fault slip associated with the Mw 7.9 aftershocks is indicated by bested 1-m orange contours.Historic earthquakes ellipse are in

fig 1. .Location of points of HF radiation estimated using back projection methods

with the data from European Seismic Union array and USA array are indicated by square s and circles respectively, with color intensity indicating time of the activity relative to the beginning of the event and symbol size proportional to amplitude of the HF radiation normalized to the peak value. The star indicates the location of the Japan Meteorological Agency epicenter .

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Conclusions

• Distribution of coseismic slip is about 50m

• This event is higher frequency seismic radiations than the Maule event 2010

• Surface convergence between Jaban and pacific ocean is about 10cm/year

• Higher rates of postseimic afterslip.

Thanx for

Attention

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