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Adisorn FoongkajornChiang Mai Seismic Station
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Abstract A drop of number of seismicity is a seismic precursor (Bath,1979). During 1960-2005, earthquakes in Sumatra-Andaman seismic belt had occurred continually. After deployment of the World Wide Standardized Seismograph Network (WWSSN) in 1960’s, instrumentally seismic data of the region has been collected systematically. According to this study more than 3000 of the earthquakes of magnitude 5 in the Sumatra-Andaman seismic belt were analyzed and mapped. About 10% decline of seismicity was found in 1990’s. Then the most destructive event of the region occurred on 26 December 2004 with consequently high seismicity.
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Scope of the study
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http://elvis.engr.wisc.edu/UER/uer96/author3/fig2.gif
SeismicPrecursors
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Seismic precursors- Decreasing Vp/Vs (10-20% change) Electrical resistivity (15% change) Number of seismicity
- Increasing (geodetic measurements) Tilt Vertical motion Volumetric strain
(Bath, 1979:298)
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First Episode of the Great Sumatra Earthquake
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Indian Plate that has played an important roll in the Sumatra-Andaman Seismic Belt
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Panoramic Scene of the Sumatra-Andaman seismic belt
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Origin of Volcanic Island Arc as Andaman and Nicobar were originated
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Epicentral Distribution in Sumatra-Andaman seismic belt during 1960-2005
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Epicentral Distribution in Sumatra-Andaman seismic belt during 1960-2005
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Number of the Earthquakes in Sumatra-Andaman Seismic Belt during 1960-2005
Year No. Change(%)
1960-1969 259
1970-1979 *
541 + 108.88
1980-1989 585 + 8.13
1990-1999 529 - 9.57
2000-2005 1238 +134.03
* Development of highly sensitive seismograph
Total 3152
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Number of the Earthquakes in Sumatra-Andaman Seismic Beltduring 1960-2005
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Magnitude Number 9 1 8 1 7 17 6 186 5 2947
Magnitude of the Earthquakes in Sumatra-Andaman seismic beltduring 1960-2005
Total 3152
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Magnitude of the Earthquakes in Sumatra-Andaman seismic beltduring 1960-2005
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Depth Distribution of the Earthquakes in Sumatra-Andaman seismic beltduring 1960-2005
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Cumulative Depth Distribution of the Earthquakes in Sumatra-Andaman seismic belt during 1960-2005
1960-1969 1960-1979
1960-1989 1960-1999
1960-2005
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Cumulative Depth Distribution of the Earthquakes in Sumatra-Andaman seismic belt during 1960-2005
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Depth Contour of the Earthquakes in Sumatra-Andaman seismic belt during 1960-2005
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Depth of the Earthquakes in Sumatra-Andaman seismic belt during 1960-2005
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Rupture, surfacewave propagationand co-seismicdisplacements measured by GPS of the great Sumatra earthquake on 26 December 2005
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Aftershock Distribution of the great Sumatra earthquake on 26 December 2005
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Magnitude of the Earthquakes in Sumatra-Andaman Seismic Belt on 26 December 2004
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Depth of the Earthquakes in Sumatra-Andaman Seismic Belt on 26 December 2004
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Major and Great Earthquakes in Sumatra-Andaman Seismic Belt during 1960-2005
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Major Earthquakes in Sumatra-Andaman Seismic Belt during 1900-1959
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Major Earthquakes in Sumatra-Andaman Seismic Belt during 1900-2005
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Conclusions According to the study more than 3000 of the earthquakes of magnitude 5 in the Sumatra-Andaman seismic belt during 1960-2005 were analyzed and mapped.
About 10% decline of seismicity was found in 1990’s. Then the most destructive event of the region occurred on 26 December 2004 with consequently high seismicity. The drop of number of seismicity is precursory potential for earthquake prediction.
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Thank you very much