American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 460169 bytes)    Cited by

GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L11307, doi:10.1029/2005GL022679, 2005

Spatial and temporal b value anomalies preceding the devastating off coast of NW Sumatra earthquake of December 26, 2004

Paiboon Nuannin

Department of Earth Sciences, Seismology, Uppsala University, Uppsala, Sweden


Ota Kulhanek

Department of Earth Sciences, Seismology, Uppsala University, Uppsala, Sweden


Leif Persson

Department of Earth Sciences, Seismology, Uppsala University, Uppsala, Sweden


Abstract

Spatial and temporal variations of b values are studied by means of 624 earthquakes in the Andaman-Nicobar Islands region during a five-year period preceding the giant shock on December 26, 2004. Sliding time and space windows containing 50 events are used. Temporal variations reveal two significant drops in b value which coincide with the occurrence of two large shocks (M s ≥ 7.0) towards the end of 2002 and with the M w = 9.0 event in 2004. The spatial distribution shows accumulation of stresses (low b) around the epicentres of the 2002 and 2004 events and an event in North Andaman. The area of high stress around the 2004 epicenter extends in NNW-SSE direction over an area about 450 km long.

Received 10 February 2005; accepted 27 April 2005; published 10 June 2005.

Index Terms: 7215 Seismology: Earthquake source observations (1240); 7223 Seismology: Earthquake interaction, forecasting, and prediction (1217, 1242); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 7240 Seismology: Subduction zones (1207, 1219, 1240).

Read Full Article (file size: 460169 bytes)    Cited by

Citation: Nuannin, P., O. Kulhanek, and L. Persson (2005), Spatial and temporal b value anomalies preceding the devastating off coast of NW Sumatra earthquake of December 26, 2004, Geophys. Res. Lett., 32, L11307, doi:10.1029/2005GL022679.