Preliminary Earthquake Report

Magnitude 9.1 - OFF THE WEST COAST OF NORTHERN SUMATRA

2004 December 26 00:58:53 UTC

Earthquake Details

This event has been reviewed by a seismologist.

Magnitude	9.1
Date-Time	Sunday, December 26, 2004 at 00:58:53 UTC Sunday, December 26, 2004 at 07:58:53 AM at epicenter Time of Earthquake in other Time Zones
Location	3.316°N, 95.854°E
Depth	30 km (18.6 miles) set by location program
Region	OFF THE WEST COAST OF NORTHERN SUMATRA
Distances	250 km (155 miles) SSE of Banda Aceh, Sumatra, Indonesia 300 km (185 miles) W of Medan, Sumatra, Indonesia 1260 km (780 miles) SSW of BANGKOK, Thailand 1590 km (990 miles) NW of JAKARTA, Java, Indonesia
Location Uncertainty	horizontal +/- 5.6 km (3.5 miles); depth fixed by location program
Parameters	NST=276, Nph=276, Dmin=654.9 km, Rmss=1.04 sec, Gp= 29°, M-type=teleseismic moment magnitude (Mw), Version=U
Source	USGS NEIC (WDCS-D)
Event ID	us2004slav

Did you feel it? Report shaking and damage at your location. You can also view a map displaying accumulated data from your report and others.

Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center:
World Data Center for Seismology, Denver

This webpage is being phased out and is no longer maintained. Please use the new Real-time Earthquake Map instead and update your bookmark. See Quick Tips & User Guide.

Versíon en Español

Earthquake Summary

Earthquake Summary Map

Felt Reports

This is the third largest earthquake in the world since 1900 and is the largest since the 1964 Prince William Sound, Alaska earthquake. In total, 227,898 people were killed or were missing and presumed dead and about 1.7 million people were displaced by the earthquake and subsequent tsunami in 14 countries in South Asia and East Africa. (In January 2005, the death toll was 286,000. In April 2005, Indonesia reduced its estimate for the number missing by over 50,000.) The earthquake was felt (IX) at Banda Aceh, (VIII) at Meulaboh and (IV) at Medan, Sumatra and (III-V) in parts of Bangladesh, India, Malaysia, Maldives, Myanmar, Singapore, Sri Lanka and Thailand. The tsunami caused more casualties than any other in recorded history and was recorded nearly world-wide on tide gauges in the Indian, Pacific and Atlantic Oceans. Seiches were observed in India and the United States. Subsidence and landslides were observed in Sumatra. A mud volcano near Baratang, Andaman Islands became active on December 28 and gas emissions were reported in Arakan, Myanmar.

Tectonic Summary

The devastating megathrust earthquake of December 26th, 2004 occurred on the interface of the India and Burma plates and was caused by the release of stresses that develop as the India plate subducts beneath the overriding Burma plate. The India plate begins its descent into the mantle at the Sunda trench which lies to the west of the earthquake's epicenter. The trench is the surface expression of the plate interface between the Australia and India plates, situated to the southwest of the trench, and the Burma and Sunda plates, situated to the northeast.

Click on images for larger versions.

FAQ - Everything Else You Want to Know about this Earthquake & Tsunami
Earthquake Information for Indonesia

Rupture area

Earthquakes rupture a patch along a fault's surface. Generally speaking, the larger the rupture patch, the larger the magnitude of the earthquake. Initial estimates based on the aftershock distribution show the magnitude 9.0 Sumatra-Andaman Islands Earthquake ruptured a patch of fault roughly the size of California, and modeling of the seismic waves show that most of the slip occurred in the southern 400 kilometers of the patch. For comparison, a magnitude 5 earthquake would rupture a patch roughly the size of New York City's Central Park.

Seismic stations

http://earthquake.usgs.gov/earthquakes/shakemap/global/shake/slav/download/stationlist.txt

Earthquake slav: 12/26/2004 00:58:53 GMT, M=9.0, N3.32 E95.85, 30.0km depth, Bias: pga=0.00 pgv=0.00

Seismic Stations

Alor_Setar: Alor Setar, Malaysia (3 responses) (CIIM)

     Coordinates: N6.11 E100.37 Dist: 583.4 km

     UNK 1.6449 cm/s  2.0365 %g

Banda_Aceh: Banda Aceh, Indonesia (12 responses) (CIIM)

     Coordinates: N5.55 E95.32 Dist: 47.2 km

     UNK 77.1984 cm/s  78.2667 %g

Bangarapet: Bangarapet, India (1 response) (CIIM)

     Coordinates: N12.97 E78.20 Dist: 1558.2 km

     UNK 0.7927 cm/s  1.0194 %g

Bengaluru: Bengaluru, India (5 responses) (CIIM)

     Coordinates: N12.97 E77.56 Dist: 1627.7 km

     UNK 2.0072 cm/s  2.4595 %g

Butterworth: Butterworth, Malaysia (2 responses) (CIIM)

     Coordinates: N5.40 E100.37 Dist: 558.5 km

     UNK 2.7970 cm/s  3.3687 %g

Chaiyaphum: Chaiyaphum, Thailand (1 response) (CIIM)

     Coordinates: N15.80 E102.04 Dist: 1015.0 km

     UNK 1.6449 cm/s  2.0365 %g

Chattagam: Chattagam, Bangladesh (2 responses) (CIIM)

     Coordinates: N22.33 E91.81 Dist: 1145.6 km

     UNK 0.7927 cm/s  1.0194 %g

Chennai: Chennai, India (52 responses) (CIIM)

     Coordinates: N13.09 E80.27 Dist: 1334.7 km

     UNK 2.4493 cm/s  2.9704 %g

Chiang_Mai: Chiang Mai, Thailand (32 responses) (CIIM)

     Coordinates: N18.80 E98.98 Dist: 955.9 km

     UNK 1.3480 cm/s  1.6862 %g

Dali: Dali, China (1 response) (CIIM)

     Coordinates: N25.70 E100.15 Dist: 1671.0 km

     UNK 0.4083 cm/s  0.5434 %g

Dehiwala-Mount_Lavinia: Dehiwala-Mount Lavinia, Sri Lanka (2 responses) (CIIM)

     Coordinates: N6.85 E79.87 Dist: 1433.9 km

     UNK 1.6449 cm/s  2.0365 %g

Dhaka: Dhaka, Bangladesh (4 responses) (CIIM)

     Coordinates: N23.70 E90.39 Dist: 1314.1 km

     UNK 1.1804 cm/s  1.4868 %g

Gampaha: Gampaha, Sri Lanka (1 response) (CIIM)

     Coordinates: N7.10 E80.00 Dist: 1413.1 km

     UNK 0.7927 cm/s  1.0194 %g

Gelugor: Gelugor, Malaysia (9 responses) (CIIM)

     Coordinates: N5.48 E100.50 Dist: 574.9 km

     UNK 2.6174 cm/s  3.1633 %g

Georgetown: Georgetown, Malaysia (8 responses) (CIIM)

     Coordinates: N5.37 E100.31 Dist: 551.2 km

     UNK 2.0072 cm/s  2.4595 %g

Habra: Habra, India (1 response) (CIIM)

     Coordinates: N22.84 E88.62 Dist: 1268.5 km

     UNK 0.7927 cm/s  1.0194 %g

Hangdong: Hangdong, Thailand (2 responses) (CIIM)

     Coordinates: N18.69 E98.92 Dist: 942.5 km

     UNK 0.7927 cm/s  1.0194 %g

Hat_Yai: Hat Yai, Thailand (7 responses) (CIIM)

     Coordinates: N7.00 E100.47 Dist: 616.3 km

     UNK 5.4309 cm/s  6.3195 %g

Ipoh: Ipoh, Malaysia (2 responses) (CIIM)

     Coordinates: N4.60 E101.07 Dist: 606.1 km

     UNK 1.3480 cm/s  1.6862 %g

Johor_Bahru: Johor Bahru, Malaysia (1 response) (CIIM)

     Coordinates: N1.48 E103.75 Dist: 909.9 km

     UNK 0.4083 cm/s  0.5434 %g

Kanjirappalli: Kanjirappalli, India (1 response) (CIIM)

     Coordinates: N9.57 E76.80 Dist: 1723.2 km

     UNK 2.6174 cm/s  3.1633 %g

Keng_Tung: Keng Tung, Myanmar (1 response) (CIIM)

     Coordinates: N21.29 E99.62 Dist: 1218.5 km

     UNK 0.7927 cm/s  1.0194 %g

Kepala_Batas: Kepala Batas, Malaysia (1 response) (CIIM)

     Coordinates: N5.52 E100.43 Dist: 569.0 km

     UNK 1.6449 cm/s  2.0365 %g

Klang: Klang, Malaysia (2 responses) (CIIM)

     Coordinates: N3.04 E101.45 Dist: 632.2 km

     UNK 0.7927 cm/s  1.0194 %g

Kochi: Kochi, India (2 responses) (CIIM)

     Coordinates: N10.02 E76.22 Dist: 1784.3 km

     UNK 0.7927 cm/s  1.0194 %g

Kolamba: Kolamba, Sri Lanka (1 response) (CIIM)

     Coordinates: N6.93 E79.85 Dist: 1433.8 km

     UNK 0.7927 cm/s  1.0194 %g

Kolar: Kolar, India (1 response) (CIIM)

     Coordinates: N13.14 E78.13 Dist: 1566.7 km

     UNK 0.7927 cm/s  1.0194 %g

Kolkata: Kolkata, India (2 responses) (CIIM)

     Coordinates: N22.57 E88.36 Dist: 1249.9 km

     UNK 0.7927 cm/s  1.0194 %g

Kota_Bahru: Kota Bahru, Malaysia (2 responses) (CIIM)

     Coordinates: N6.12 E102.24 Dist: 779.8 km

     UNK 0.7927 cm/s  1.0194 %g

Kozhikkod: Kozhikkod, India (1 response) (CIIM)

     Coordinates: N11.26 E75.78 Dist: 1825.0 km

     UNK 0.7927 cm/s  1.0194 %g

Krung_Thep: Krung Thep, Thailand (27 responses) (CIIM)

     Coordinates: N13.73 E100.50 Dist: 784.6 km

     UNK 2.2921 cm/s  2.7893 %g

Kuala_Lumpur: Kuala Lumpur, Malaysia (16 responses) (CIIM)

     Coordinates: N3.16 E101.71 Dist: 660.5 km

     UNK 2.1449 cm/s  2.6192 %g

Kulim: Kulim, Malaysia (3 responses) (CIIM)

     Coordinates: N5.36 E100.55 Dist: 576.0 km

     UNK 1.3480 cm/s  1.6862 %g

Kuta: Kuta, Indonesia (1 response) (CIIM)

     Coordinates: S8.72 E115.17 Dist: 2533.2 km

     UNK 0.4083 cm/s  0.5434 %g

Mae_Hong_Son: Mae Hong Son, Thailand (2 responses) (CIIM)

     Coordinates: N19.27 E97.93 Dist: 935.1 km

     UNK 1.6449 cm/s  2.0365 %g

Mae_Sai: Mae Sai, Thailand (4 responses) (CIIM)

     Coordinates: N20.43 E99.88 Dist: 1156.3 km

     UNK 0.7927 cm/s  1.0194 %g

Maerim: Maerim, Thailand (1 response) (CIIM)

     Coordinates: N18.91 E98.94 Dist: 962.8 km

     UNK 1.4405 cm/s  1.7957 %g

Maha_Nuwara: Maha Nuwara, Sri Lanka (5 responses) (CIIM)

     Coordinates: N7.29 E80.63 Dist: 1340.5 km

     UNK 0.7927 cm/s  1.0194 %g

Male: Male, Maldives (24 responses) (CIIM)

     Coordinates: N4.17 E73.50 Dist: 2195.9 km

     UNK 2.9889 cm/s  3.5874 %g

Mandalay: Mandalay, Myanmar (2 responses) (CIIM)

     Coordinates: N21.98 E96.09 Dist: 1139.0 km

     UNK 2.6174 cm/s  3.1633 %g

Matale: Matale, Sri Lanka (1 response) (CIIM)

     Coordinates: N7.47 E80.62 Dist: 1336.9 km

     UNK 2.0072 cm/s  2.4595 %g

Matara: Matara, Sri Lanka (1 response) (CIIM)

     Coordinates: N5.96 E80.53 Dist: 1393.0 km

     UNK 0.4083 cm/s  0.5434 %g

Medan: Medan, Indonesia (5 responses) (CIIM)

     Coordinates: N3.59 E98.67 Dist: 325.2 km

     UNK 3.1939 cm/s  3.8203 %g

Meulaboh: Meulaboh, Indonesia (3 responses) (CIIM)

     Coordinates: N4.14 E96.12 Dist: 77.0 km

     UNK 88.1546 cm/s  88.7609 %g

Mumbai: Mumbai, India (2 responses) (CIIM)

     Coordinates: N18.96 E72.82 Dist: 2247.9 km

     UNK 0.4083 cm/s  0.5434 %g

Naihati: Naihati, India (1 response) (CIIM)

     Coordinates: N22.91 E88.43 Dist: 1282.5 km

     UNK 1.1047 cm/s  1.3962 %g

Padang: Padang, Indonesia (1 response) (CIIM)

     Coordinates: S0.95 E100.35 Dist: 693.6 km

     UNK 0.7927 cm/s  1.0194 %g

Palakkad: Palakkad, India (1 response) (CIIM)

     Coordinates: N10.78 E76.65 Dist: 1732.9 km

     UNK 0.4083 cm/s  0.5434 %g

Petaling_Jaya: Petaling Jaya, Malaysia (3 responses) (CIIM)

     Coordinates: N3.10 E101.62 Dist: 650.7 km

     UNK 0.7927 cm/s  1.0194 %g

Phuket: Phuket, Thailand (14 responses) (CIIM)

     Coordinates: N7.88 E98.38 Dist: 429.4 km

     UNK 3.1939 cm/s  3.8203 %g

Port_Blair: Port Blair, India (1 response) (CIIM)

     Coordinates: N11.67 E92.76 Dist: 17.2 km

     UNK 24.9859 cm/s  26.8594 %g

Pune: Pune, India (1 response) (CIIM)

     Coordinates: N18.53 E73.84 Dist: 2130.7 km

     UNK 0.4083 cm/s  0.5434 %g

Samut_Songkhram: Samut Songkhram, Thailand (1 response) (CIIM)

     Coordinates: N13.42 E100.00 Dist: 724.4 km

     UNK 1.6449 cm/s  2.0365 %g

Sankamphaeng: Sankamphaeng, Thailand (1 response) (CIIM)

     Coordinates: N18.74 E99.12 Dist: 960.1 km

     UNK 0.7927 cm/s  1.0194 %g

Seremban: Seremban, Malaysia (2 responses) (CIIM)

     Coordinates: N2.71 E101.95 Dist: 690.2 km

     UNK 2.6174 cm/s  3.1633 %g

Sidoarjo: Sidoarjo, Indonesia (1 response) (CIIM)

     Coordinates: S7.45 E112.71 Dist: 2227.5 km

     UNK 0.7927 cm/s  1.0194 %g

Singapore: Singapore, Singapore (11 responses) (CIIM)

     Coordinates: N1.30 E103.85 Dist: 925.4 km

     UNK 0.7927 cm/s  1.0194 %g

Sri_Jayawardenepura: Sri Jayawardenepura, Sri Lanka (4 responses) (CIIM)

     Coordinates: N6.89 E79.90 Dist: 1429.6 km

     UNK 0.7927 cm/s  1.0194 %g

Sungai_Ara: Sungai Ara, Malaysia (7 responses) (CIIM)

     Coordinates: N5.33 E100.27 Dist: 545.6 km

     UNK 3.4130 cm/s  4.0684 %g

Sungai_Petani: Sungai Petani, Malaysia (1 response) (CIIM)

     Coordinates: N5.65 E100.48 Dist: 578.8 km

     UNK 2.0072 cm/s  2.4595 %g

Taiping: Taiping, Malaysia (1 response) (CIIM)

     Coordinates: N4.86 E100.72 Dist: 576.4 km

     UNK 0.7927 cm/s  1.0194 %g

Tanjong_Bunga: Tanjong Bunga, Malaysia (5 responses) (CIIM)

     Coordinates: N5.47 E100.27 Dist: 550.5 km

     UNK 2.0072 cm/s  2.4595 %g

Tanjung_Agung: Tanjung Agung, Indonesia (1 response) (CIIM)

     Coordinates: S3.93 E103.80 Dist: 1199.0 km

     UNK 0.7927 cm/s  1.0194 %g

Trang: Trang, Thailand (1 response) (CIIM)

     Coordinates: N7.56 E99.61 Dist: 539.5 km

     UNK 0.7927 cm/s  1.0194 %g

Trece_Martires: Trece Martires, Philippines (1 response) (CIIM)

     Coordinates: N14.28 E120.86 Dist: 2977.5 km

     UNK 0.4083 cm/s  0.5434 %g

Visakhapatnam: Visakhapatnam, India (8 responses) (CIIM)

     Coordinates: N17.73 E83.30 Dist: 1175.7 km

     UNK 1.5393 cm/s  1.9123 %g

Wattala: Wattala, Sri Lanka (1 response) (CIIM)

     Coordinates: N6.97 E79.89 Dist: 1428.4 km

     UNK 0.7927 cm/s  1.0194 %g

Yangon: Yangon, Myanmar (1 response) (CIIM)

     Coordinates: N16.79 E96.15 Dist: 603.4 km

     UNK 1.2614 cm/s  1.5834 %g

Yunjinghong: Yunjinghong, China (1 response) (CIIM)

     Coordinates: N21.97 E100.81 Dist: 1350.9 km

     UNK 1.1047 cm/s  1.3962 %g

Explanation of Flags

M - Manually flagged

T - Outlier

G - Amplitude off scale or below noise

I - Incomplete data

N - Not in list of known stations

Magnitude 9.1 - OFF THE WEST COAST OF NORTHERN SUMATRA

http://earthquake.usgs.gov/earthquakes/eqinthenews/2004/us2004slav/

This webpage is being phased out and is no longer maintained. Please use the new Real-time Earthquake Map instead and update your bookmark. See Quick Tips & User Guide.

2004 December 26 00:58:53 UTC

Details

Summary

Maps

Scientific & Technical

Additional Info

Earthquake Details

This event has been reviewed by a seismologist.

Magnitude 9.1

Date-Time

Sunday, December 26, 2004 at 00:58:53 UTC

Sunday, December 26, 2004 at 07:58:53 AM at epicenter

Time of Earthquake in other Time Zones

Location 3.316°N, 95.854°E

Depth 30 km (18.6 miles) set by location program

Region OFF THE WEST COAST OF NORTHERN SUMATRA

Distances 250 km (155 miles) SSE of Banda Aceh, Sumatra, Indonesia

300 km (185 miles) W of Medan, Sumatra, Indonesia

1260 km (780 miles) SSW of BANGKOK, Thailand

1590 km (990 miles) NW of JAKARTA, Java, Indonesia

Location Uncertainty horizontal +/- 5.6 km (3.5 miles); depth fixed by location program

Parameters NST=276, Nph=276, Dmin=654.9 km, Rmss=1.04 sec, Gp= 29°,

M-type=teleseismic moment magnitude (Mw), Version=U

Source

USGS NEIC (WDCS-D)

Event ID us2004slav

Felt Reports

Tectonic Summary

Magnitude 9.1 OFF THE WEST COAST OF NORTHERN SUMATRA

Sunday, December 26, 2004 at 00:58:53 UTC

The devastating earthquake of 26 December 2004 occurred as thrust-faulting on the interface of the India plate and the Burma plate. In a period of minutes, the faulting released elastic strains that had accumulated for centuries from ongoing subduction of the India plate beneath the overriding Burma plate.

In a broad sense, the India and Australian plates move toward the north- northeast with respect to the interior of the Eurasia plate with velocities of about 60 mm/y in the region of the earthquake. In the region of northern Sumatra and the Nicobar Islands, most of the relative motion of India/Australia and the Eurasia plate is accommodated at the Sunda trench and within several hundred kilometers to the east of the Sunda trench, on the boundaries of the Burma plate. The direction in which India/Australia converges toward Eurasia is oblique to the trend of the Sunda trench. The oblique motion is partitioned into thrust-faulting and strike-slip faulting. The thrust faulting occurs on the interface between the India plate and the western margin of the Burma plate and involves slip directed at a large angle to the orientation of the trench. The strike-slip faulting occurs on the eastern boundary of the Burma plate and involves slip directed approximately parallel to the trench. The 26 December main shock occurred as the result of thrust faulting on the western Burma-plate boundary, but many strike-slip faulting aftershocks occurred on the eastern plate boundary.

Currently available models of the 26 December main-shock fault displacement differ in many interesting details, but are consistent in implying that fault- rupture propagated to the northwest from the epicenter and that substantial fault-rupture occurred hundreds of kilometers northwest of the epicenter. The data upon which the modeling is based do not permit confident resolution of the extent of rupture beyond about 500 km northwest of the main-shock epicenter. The width of the earthquake rupture, measured perpendicular to the Sunda trench, is estimated to have been about 150 kilometers and the maximum displacement on the fault plane about 20 meters. The sea floor overlying the thrust fault would have been uplifted by several meters as a result of the earthquake.

The zone of aftershocks to the 26 December earthquake is over 1300 km long. Because aftershocks occur on and very near the fault-planes of main shocks, the length of the aftershock zone suggests that main-shock fault-rupture may have extended north of the epicenter by an amount significantly larger than 500 km. However, a great earthquake may also trigger earthquake activity on faults that are distinct from the main-shock fault plane and separated from it by tens or even hundreds of kilometers. We will not know until further analysis how much of the 26 December aftershock zone may correspond to activity in the immediate vicinity of the main-shock rupture, and how much may correspond to activity remote from the main-shock rupture.

Since 1900, earthquakes similarly sized or larger than the 26 December earthquake have been the magnitude 9.0 1952 Kamchatka earthquake, the magnitude 9.1 1957 Andreanof Islands, Alaska, earthquake, the magnitude 9.5 1960 Chile earthquake, and the magnitude 9.2 1964 Prince William Sound, Alaska, earthquake. All of these earthquakes, like the one on 26 December, were mega-thrust events, occurring where one tectonic plate subducts beneath another. All produced destructive tsunamis, although deaths and damage from the 26 December tsunami far exceed those caused by tsunamis associated with the earlier earthquakes.

Finite Fault Model

Magnitude 9.1 OFF THE WEST COAST OF NORTHERN SUMATRA

Sunday, December 26, 2004 at 00:58:53 UTC

Preliminary Rupture Model

Contributed by Chen Ji, Caltech

DATA Process and Inversion

We used the GSN broadband data downloaded from the IRIS DMC. We analyzed 15 teleseismic P waveforms and 13 SH waveforms selected based upon data quality and azimuthal distribution. Waveforms are first converted to displacement by removing the instrument response and then are used to constrain the slip history based on a finite fault inverse algorithm (Ji et al, 2002). We use the hypocenter from the USGS (Lon.=95.78 deg.; Lat.=3.30 deg.). The fault planes are defined by slightly modifying the quick moment tensor solution from HARVARD (strike=320 deg. and dip =11 deg.)

Result

The seismic moment release on this plane is 3.57x10**29 dyne.cm using a 1D crustal model interpolated from CRUST2.0 (Bassin et al., 2000). The total rupture duration is 200 sec and the peak slip is about 20 m. The rupture propagates northwestward for nearly 400 km with a speed of 2.0 km/sec.

Cross-section of slip distribution

...

Figure: The big black arrow shows the fault's strike. The colors show the slip amplitude and white arrows indicate the direction of motion of the hanging wall relative to the footwall. Contours show the rupture initiation time and the red star indicates the hypocenter location.

Comparison of data and synthetic seismograms

...

Figure: The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micrometers. The number above the beginning of each trace is the source azimuth and below it is the epicentral distance.

...

Figure: Surface projection of the slip distribution. The ocean is plotted in blue and land is plotted in green. The black line indicates the plate boundary (data from Dr. Lisa Gahagan, Paleo-Oceanographic Mapping Project at University of Texas at Austin).

CJ's Comments:

It is noteworthy that the seismic data we used only could constrain the slip in first 220 sec. Hence, we can not totally rule out later, smaller slip if it occurred further north.

We notice that the location of the biggest asperity correlates well with a nearly 30 degree bend of the subducted India plate. In the figure shown below, we let the fault plane rotate 7 deg. counterclockwise to match the 0 and 50 km isodepth contours of Gundmundsson and Sambridge (1998). It is clear that the northern boundary of the biggest asperity is along the hinge line of the slab (indicated by arrows). The pink circles are big aftershocks (>5) downloaded from the NEIC. Five of them locate at the north boundary as well. The large slip associating with the bend of the fault plane is a common feature, e.g., 1999 Chi-Chi earthquake (Ji et al., 2003, JGR).

This result also suggests that we need use at least two fault segments with different strikes to model the rupture of this event. We are currently working on such a model and we will provide an update as it becomes available.

...

(below) Predicted static surface displacements (in meters) for vertical (left) and horizontal (right) components of motion. Based on the single-place finite fault source model shown.

...

Download (Slip Distribution): SUBFAULT FORMAT

References

Ji, C., D.J. Wald, and D.V. Helmberger, Source description of the 1999 Hector Mine, California earthquake; Part I: Wavelet domain inversion theory and resolution analysis, Bull. Seism. Soc. Am., Vol 92, No. 4. pp. 1192-1207, 2002.

Bassin, C., Laske, G. and Masters, G., The Current Limits of Resolution for Surface Wave Tomography in North America, EOS Trans AGU, 81, F897, 2000.

Gundmundsson, O. and M. Sambridge, A regionalized upper mantle (RUM) seismic model, JGR, v. 103, No. B4, 7121-7136, 1998.

Acknowledgement

This work is supported by Gordon and Betty Moore Foundation Caltech Tectonic Observatory, National Earthquake Information Center (NEIC) of United States Geological Survey, and Caltech's Seismological Laboratory.