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Ömer AYDAN

Sept. 30, 2009 PARIAMAN-PADANG EARTHQUAKE

Ömer AYDANTokai University, Shizuoka, Japan

JAEE

JSCE-EEC

EWBJ

CONTENT

1) TECTONICS AND SEISMICITY

2) REGIONAL GEOLOGY, TECTONICS AND SEISMICITY

3) FAULTING MECHANISM AND SLIP

4) LOCAL GEOLOGY AND GEOTECHNICAL CONDITIONS

5) STRONG MOTIONS

6) SLOPE FAILURES AND ROCK FALLS AND DAMAGE TO ROADWAYS AND RAILWAYS IN MOUNTAINOUS REGIONREGION

7) RIVER EMBANKMENTS AND WAVE BREAKS

8) DAMAGE TO REPAIRED BUILDINGS IN 2007 BY 2009 EQ.

TECTONICS OF INDONESIA & ITS CLOSE VICINITY SEISMIC GAPS IN/AROUND INDONESIA

M7.6

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19 Segments by Sieh and NatawidjajaSeismic GapsSunda (150km), Kumering (150km),

Sumatra Fault Zone

Dikit (60km), Sumpur (35km), Burumun (115km), Tripa (180km), Aceh(200km) and Seulimeum (120 )

Padang

(120km)The expected moment magnitudes of earthquakes for Tripa, Aceh and Seulimeum segments would range between 7.4and 7.8 and return period 160 to 400 years

Possible Seismic Gaps

ANTICIPATED MEGA EARTHQUAKE

There is a large seismic gap between 2007 and 2005 rupture zones. The estimated magnitude would be more than 8.7. This earthquake will hit West Sumatra and the possibility of huge tsunami waves striking Padang City is quite high

M7.6 Earthquake did increase the

Measures against Ground Shaking

Measures against Tsunami

qpossibility of the M8.7 Mega Earthquake

Anticipated Focal Mechanism of the M8.7 Mega Earthquake

FAULTING MECHANISM

The strike of Sep. 30, 2009 earthquake is perpendicular to that of the anticipated earthquake.

Situation is similar to the anticipated Tokai Earthquake in Japan

Yagi, 2009

Mw=7.6

Vr＝4.5km/s

Tr=12ｓ71/51/135

SLIP

71/51/135

USGS, 2009

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GEOLOGY OF WEST SUMATRA

Detailed Geology

Qpt: Quaternary pyroclastic fans and tuff deposits

Qal: Quaternary alluvial deposits

Amax (%G) Vmax (cm/s)

Amax > 0.28G Vmax > 35cm/sUSGS, 2009

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SLOPE FAILURES

Failure of steep slopes with small height (4-6m) Failure of roads in mountainous region (Padang Alai region)

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Block toppling and subsequent rockfalls along Padang-Bukittinggi Roadway

Rockfalls on Padang-Bukittinggi RoadwayRockfalls on Railway Line and Padang-Bukittinggi Roadway