Magnitude analysis of aftershocks of the Mw 9.3 Sumatra-Andaman Earthquake recorded at the temporary PSU Seismic Station in Phang nga, Thailand

• Main Authors: Helmut Düerrast, Warawutti Lohawijarn, Nawarat Setapong
• Format: Article
• Language: English
• Published: Prince of Songkla University 2008-03-01
• Series: Songklanakarin Journal of Science and Technology (SJST)
• Subjects: Earthquake; body wave magnitude; moment magnitude; Sumatra-Andaman Earthquake; tsunami warning
• Online Access: http://rdo.psu.ac.th/sjst/ejournal/journal/30-2/0125-3395-30-2-191-199.pdf

After the M_w 9.3 Sumatra-Andaman Earthquake on 26 December 2004, a temporary broadband seismic station was set up at the Khao Chang Telecommunication Station in Phang nga Province, Southern Thailand, in order to monitor aftershocks in an area bounded by 0^o-20^o N, and 90^o-100^o E. Altogether 98 events were identified during the study period from 1^st to 12^th January 2005; but six of these events are not listed in the catalog of the United States Geological Survey (USGS/ NEIC). Body wave magnitudes (m_b) and moment magnitudes (M_w) of the events were determined and compared with USGS magnitudes. For m_b, the PSU values are 0.215 higher than the USGS values, whereas for M_w, the PSU values are 0.268 lower than the USGS values. Differences in m_b may result from differences in time windows chosen for the maximum amplitude determination, or from accuracy of the Q-value. Differences in M_w may result from assumptions made on velocity, attenuation and determination of the low-frequency part of the seismic spectrum. However, these differences are comparatively small considering that the USGS data are network values whereas the PSU data are from a single station.