Probabilistic Seismic Hazard Analysis in Thailand and Adjacent

Document Sample
Probabilistic Seismic Hazard Analysis in Thailand and Adjacent Powered By Docstoc
					               Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG;
                                                                                                                      November 24-26, 2008, Bangkok, Thailand




Probabilistic Seismic Hazard Analysis in Thailand and Adjacent Areas by
Using Regional Seismic Source Zones

Santi Pailoplee1*, Yuichi Sugiyama2 and Punya Charusiri1

1.	 Earthquake	and	Tectonic	Geology	Research	Unit	(EATGRU),	c/o	Department	of	Geology,	Faculty	of	Science,	Chulalongkorn	
	 University,	Bangkok	10330,	Thailand
2.	 Active	Fault	Research	Center,	National	Institute	of	Advanced	Industrial	Science	and	Technology	(AIST)	7,	1-1-1	Higashi,		
	 Tsukuba,	Ibaraki	305-8567,	Japan
*Corresponding	author	e-mail:	pailoplee.s@gmail.com


Extended Abstract

We	conducted	probabilistic	seismic	hazard	analysis	for	Thailand	and	adjacent	areas	by	using	a	method	proposed	by	
Cornell	(1968).	We	produced	seismic	hazard	maps	showing	peak	ground	acceleration	(PGA)	and	Modified	Mercalli	
Intensity	(MMI).	Twenty-one	seismic	source	zones	(Charusiri	et	al.,	2005)	(Fig.	1),	which	cover	all	of	Thailand	and	extend	
into	adjacent	areas,	were	employed.	The	seismicity	data	used	in	this	study	was	a	merged	data	set	covering	1963-2007	
from	several	international	earthquake	catalogues	and	a	single	Thai	catalogue.

We	selected	the	strong	ground-motion	attenuation	model,	proposed	by	Kobayashi	et	al.	(2000)	(Fig.	2),	for	this	study	
by	applying	121	existing	attenuation	models	(Douglas,	2001)	to	recorded	strong	ground-motion	data	and	choosing	
the	model	that	best	fit	our	data.	Seismic	hazard	analysis	was	carried	out	for	2,521	grid	points	on	a	0.25°	x	0.25°	mesh	
within	a	rectangle	defined	by	longitudes	92°-106°E	and	latitudes	0°-21°N.

The	resulting	PGA	maps	for	2%	probability	of	exceedance	for	return	periods	of	10	to	100	years	suggest	that	ground	
motion	of	0.4	to	1	g	may	occur	in	northern	and	western	Thailand	and	from	0	to	0.4	g	in	other	parts	of	our	study	area	(Fig.	
3).	The	maximum	MMI	in	northern,	western,	and	southern	Thailand	may	reach	levels	VI,	V,	and	IV,	respectively	(Fig.	4).

Our	result	seems	to	be	slightly	different	from	that	of	Palasri	(2006).	The	seismic	hazard	analysis	presented	here	is	
an	important	step	toward	an	accurate	evaluation	of	seismic	hazard	potential	in	Thailand	and	adjacent	areas.	Further	
work	is	needed	to	refine	the	analysis.	More	observations	of	strong	ground	motion	in	the	region	are	needed	and	further	
seismo-tectonic	research	should	be	encouraged.

Key words: seismic hazard analysis; probabilistic approach; seismic source zone; earthquake catalogue;
Thailand




                                                                                                                                                        405
Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG;
November 24-26, 2008, Bangkok, Thailand




                                                                                                   Figure 1	     Location	map	showing	21	seismic	source	      	
                                                                                                   	    	        zones	covering	Thailand	(gray	shading)	
                                                                                                   	    	        and	adjacent	areas	(Charusiri	et	al.,	2005).




                                                                                                                      Figure 2	     Comparison	of	published	
                                                                                                                      	    	        strong	ground-motion	              	
                                                                                                                      	    	        a t t e n u a t i o n 	 m o d e l s	
                                                                                                                      	    	        with	 recorded	 strong	            	
                                                                                                                      	    	        ground-motion	data	(blue	
                                                                                                                      	    	        s q u a r e s ) 	 f o r 	 a 	 5 . 1	
                                                                                                                      	    	        earthquake	(after	Palasri,	
                                                                                                                      	    	        2006).




406
               Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG;
                                                                                                                      November 24-26, 2008, Bangkok, Thailand




     a.     2% probability of exceedance in 10-year                             b.    2% probability of exceedance in 30-year
            return period                                                             return period




     c.     2% probability of exceedance in 50-year                             d.    2% probability of exceedance in 100-year
            return period                                                             return period


Figure 3	   Probabilistic	seismic	hazard	maps	of	Thailand	and	adjacent	areas	showing	the	distribution	of	Peak	Ground	Acceleration	(PGA)	that	
	    	      exceeds	2%	probabilities	for	return	periods	of	10,	30,	50,	and	100	years.




                                                                                                                                                        407
Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG;
November 24-26, 2008, Bangkok, Thailand




a.    % of ground shaking               IV (MMI) in 50-year                        b.     % of ground shaking              V (MMI) in 50-year
      return period                                                                       return period




c.    % of ground shaking               VI (MMI) in 50-year                        d.     % of ground shaking              VII (MMI) in 50-year
      return period                                                                       return period


Figure 4.		 Probabilistic	seismic	hazard	maps	of	Thailand	and	adjacent	areas	showing	the	probabilities	(%)	that	ground	shaking	will	be	equal	
	    	      to	or	greater	than	levels	IV,	V,	VI,	and	VII	(Modified	Mercalli	Intensity)	for	return	periods	of	50	years.




408
             Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG;
                                                                                                                    November 24-26, 2008, Bangkok, Thailand




References
Charusiri, P., Choowong, M., Charoentitirat, T., Jankaew, K., Chutakositkanon, V., Kanjanapayont, P., 2005. Geological
    and physical effect evaluation in the tsunami damage area for restoration and warning system. Technical report
    submitted to Department of Mineral Resources, Bangkok, Thailand. (unpublished)
Cornell, C.A., 1968. Engineering seismic risk analysis. Bulletin of the Seismological Society of America 58,
    1583–1606.
Douglas, J., 2001. A comprehensive worldwide summary of strong-motion attenuation relationships for peak ground
    acceleration and spectral ordinates (1969–2000). Imperial College of Science, Technology and Medicine, Civil
    Engineering Department, London. ESEE Report 01-1, 138 p.
Kobayashi, S., Takahashi, T., Matsuzaki, S., Mori, M., Fukushima, Y., Zhao, J.X., Somerville, P.G., 2000. A spectral
    attenuation model for Japan using digital strong motion records of JMA87 type. Proceedings of the 12th World
    Conference on Earthquake Engineering, 30 January – 4 February 2000. Auckland, New Zealand.
Palasri, C., 2006. Probabilistic seismic hazard map of Thailand. M.S. thesis, Department of Civil Engineering, Faculty
    of Engineering, Chulalongkorn University, Thailand.




                                                                                                                                                      409