- journal_title：Bulletin of the Seismological Society of America
- Contributor：Paramesh Banerjee ; Fred Pollitz ; B. Nagarajan ; Roland Bürgmann
- Publisher：Seismological Society of America
- Date：2007-
- Format：text/html
- Language：en
- Identifier：10.1785/0120050609
- journal_abbrev：Bulletin of the Seismological Society of America
- issn：0037-1106
- volume：97
- issue：1A
- firstpage：S86
- section：Articles
Static offsets produced by the 26 December 2004 M ∼9 Sumatra– Andaman earthquake as measured by Global Positioning System (<span class="sc">gpsspan>) reveal a large amount of slip along the entire ≳1300 km-long rupture. Most seismic slip inversions place little slip on the Andaman segment, whereas both near-field and far-field <span class="sc">gpsspan> offsets demand large slip on the Andaman segment. We compile available datasets of the static offset to render a more detailed picture of the static-slip distribution. We construct geodetic offsets such that postearthquake positions of continuous <span class="sc">gpsspan> sites are reckoned to a time 1 day after the earthquake and campaign <span class="sc">gpsspan> sites are similarly corrected for postseismic motions. The newly revised slip distribution (M<sub>wsub> 9.22) reveals substantial segmentation of slip along the Andaman Islands, with the southern quarter slipping ∼15 m in unison with the adjacent Nicobar and northern Sumatran segments of length ∼700 km. We infer a small excess of geodetic moment relative to the seismic moment. A similar compilation of <span class="sc">gpsspan> offsets from the 28 March 2005 Nias earthquake is well explained with dip slip averaging several meters (M<sub>wsub> = 8.66) distributed primarily at depths greater than 20 km.
Online material: Offset estimation procedure, comparison of results to other studies and simpler solutions, and tables of coseismic offsets.