| Abstract: | Published areas of high coseismic slip, or asperities, for 29 of the largest Circum-Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free-air gravity, bathymetry, and seismic profiling. On average, 71% of an earthquake‘s seismic moment and 79% of its asperity area occur beneath the prominent gravity low outlining the deep-sea terrace; 57% of an earthquake‘s asperity area, on average, occurs beneath the forearc basins that lie within the deep-sea terrace. In SW Japan, slip in the 1923, 1944, 1946, and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350??C isotherm on the plate boundary, the inferred downdip limit of the locked zone. Basin-centered coseismic slip also occurred along the Aleutian, Mexico, Peru, and Chile subduction zones but was ambiguous for the great 1964 Alaska earthquake. Beneath intrabasin structural highs, seismic slip tends to be lower, possibly due to higher temperatures and fluid pressures. Kilometers of late Cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion. The deep-sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes. Basin-centered asperities could indicate a link between subsidence, subduction erosion, and seismogenesis. Whatever the cause, forearc basins may be useful indicators of long-term seismic moment release. The source zone for Cascadia‘s 1700 A.D. earthquake contains five large, basin-centered gravity lows that may indicate potential asperities at depth. The gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore, except in northwestern Washington, where the low extends landward beneath the coast. Transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes. Published in 2003 by the American Geophysical Union. |
| Genre: | Article |
| ProdID: | 70025608 |
| Citation Author: | Wells, R. E.; Blakely, R. J.; Sugiyama, Y.; Scholl, D. W.; Dinterman, P. A. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | |
| Citation Issue: | 10 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Journal of Geophysical Research B: Solid Earth |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Basin-centered asperities in great subduction zone earthquakes: A link between slip, subsidence, and subduction erosion?; 2003; Article; Journal; Journal of Geophysical Research B: Solid Earth; Wells, R. E.; Blakely, R. J.; Sugiyama, Y.; Scholl, D. W.; Dinterman, P. A. |
| Citation Start Page: | |
| Citation Volume: | 108 |
| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Basin-centered asperities in great subduction zone earthquakes: A link between slip, subsidence, and subduction erosion?; 2003; Article; Journal; Journal of Geophysical Research B: Solid Earth; Wells, R. E.; Blakely, R. J.; Sugiyama, Y.; Scholl, D. W.; Dinterman, P. A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 2003 00:00 -0600 |
| Publisher: | |
