scec annual meeting, palm springs, california, september 2017 · scec annual meeting, palm springs,...
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Author
6. Conclusions
2. Seismotectonic setup
4.1 Source parameters
Abstract
Synthetic ground motions of the 8 October 2005 Kashmir earthquake (Mw 7.6): a stochastic finite fault element approach
Hamid Sana SCEC Annual Meeting, Palm Springs, California, September 2017
Synthetic ground motions of the 8 October 2005 Kashmir earthquake (Mw 7.6) were generated in the Kashmir basin, NW Himalaya. This earthquake caused paramount amount of damage to life and property. It resulted in death of 86,000 people and destroyed property amounting to millions of dollars. The stochastic finite fault element method with dynamic corner frequency was used to simulate the ground motions of this earthquake throughout the Kashmir basin. The synthetic ground motions were generated at engineering bed rock and later transmitted to the surface using shear wave velocity (Vs30) of the alluvium in the basin. The results are in agreement with the damage trajectory of the earthquake and to the estimates of the ground motion from the field investigations. These results are thus useful in carryout the detailed seismic hazard assessment of the Kashmir basin. Especially when destructive earthquakes like 1555 (Mw 7.6) and 1885 (Mw 6.3) have been reported in the historical archives.
Postdoctoral Fellow, Department of Neotectonics and Thermochronology, Institute of Rock Structure and Mechanics, Czech Academy of Sciences, Prague 18209 Czech Republic.email: [email protected]; [email protected]
1. Introduction Kashmir valley is a northwest-southeast directed, Neogene-Quaternary tectonic basin in the NW
Himalaya . Due to the active tectonic set-up in and around this basin, this region has been struck by various
destructive earthquakes (Ambraseys and Douglas, 2004) The 8 October 2005 Kashmir earthquake (Mw 7.6) was the most recent earthquake that shook the
region. Here the synthetic ground motions of this earthquake are presented at engineering bedrock and at
the surface level in the Kashmir basin. The Stochastic finite fault element method with dynamic corner frequency was used to simulate the
synthetic ground motions. This modelling technique was basically introduced by Boore (1983), since then it has been
modified with very useful changes like the finite-fault modelling of Beresnev & Atkinson (1997) and the dynamic corner frequency approach of Motezidian & Atkinson (2005).
The synthetic ground motions of the 8 October 2005 Kashmir earthquake (Mw 7.6) are consistent with the reported ground motions and the damage pattern in the Kashmir basin.
The results of this study should be incorporated while assessing the seismic hazard of the Kashmir basin from recent instrumental as well as historical earthquakes.
Map showing location of the Kashmir basin and surroundings
Seismotectonic Sketch map of Kashmir. Region.
The synthetic ground motion modelling is usually carried out either by the adopting the Frequency-Wave number integration (F-K) method or the widely used stochastic approach.
The stochastic method is preferred here due to ease in the compilation of the strong-motion simulation parameters.
Motezidian & Atkinson (2005) was used in this study, as Beresnev & Atkinson (1997) is not sensitive to higher frequencies
Parameter 2005 Kashmir earthquake
Strike 334°Dip 34°
Hypocentre 34.38°N/73.47°E
Focal Depth 12 KmMagnitude Mw 7.6
Fault Length/Width 97/32 KmStress Drop 91.5 bar
Shear Wave Velocity 3.12 Km/sCrustal Density 3.20 g/cm3
Qs 253f0.8
K 0.03
5.1 Synthetic Seismograms
5.2 Synthetic ground motion at bedrock
5.3 Synthetic ground motion at surface
3. Methodology
4.2 Shear wave velocity
ReferencesAmbraseys, N. and Douglas, J. (2004). Geophysical Journal International, 159:165-206.Boore, D. M. (1983). Bulletin of the Seismological Society of America ,73:1865–1894.Beresnev, I. A. and Atkinson, G. (1997). Bulletin of the Seismological Society of America, 87: 67-84.Motazedian, D. and Atkinson, G. (2005). Bulletin of the Seismological Society of America, 95: 995-1010.
Shear wave velocity (Vs30) distribution map of the Kashmir basin alluvium
4. Input Parameters
5. Results
Synthetic seismogram
s at Bedrock
Synthetic seismogram
s at Surface
Synthetic ground motions of the 8 October 2005 Kashmir earthquake (Mw 7.6) at surface in Kashmir basin.
NEHRP site classes
Synthetic ground motions of the 8 October 2005 Kashmir earthquake (Mw 7.6) at the bedrockin Kashmir basin.