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The 1987 Whittier Narrows, California, earthquake: A Metropolitan shock

Hauksson, Egill and Stein, Ross S. (1989) The 1987 Whittier Narrows, California, earthquake: A Metropolitan shock. Journal of Geophysical Research B, 94 (B7). pp. 9545-9547. ISSN 0148-0227. doi:10.1029/JB094iB07p09545.

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Just 3 hours after the Whittier Narrows earthquake struck, it became clear that a heretofore unseen geological structure was seismically active beneath metropolitan Los Angeles. Contrary to initial expectations of strike-slip or oblique-slip motion on the Whittier fault, whose north end abuts the aftershock zone, the focal mechanism of the mainshock showed pure thrust faulting on a deep gently inclined surface [Hauksson et al., 1988]. This collection of nine research reports spans the spectrum of seismological, geodetic, and geological investigations carried out as a result of the Whittier Narrows earthquake. Although unseen, the structure was not unforeseen. Namson [1987] had published a retrodeformable geologic cross section (meaning that the sedimentary strata could be restored to their original depositional position) 100 km to the west of the future earthquake epicenter in which blind, or subsurface, thrust faults were interpreted to be active beneath the folded southern Transverse Ranges. Working 25 km to the west, Hauksson [1987] had also found a surprising number of microearthquakes with thrust focal mechanisms south of the Santa Monica mountains, another clue to a subsurface system of thrust faults. Finally, Davis [1987] had presented a preliminary cross section only 18 km to the west of Whittier Narrows that identified as "fault B" the thrust that would rupture later that year. Not only was the earthquake focus and its orientation compatible with the 10–15 km depth and north dipping orientation of Davis' proposed thrust, but fault B appears to continue beneath the northern flank of the Los Angeles basin, skirting within 5 km of downtown Los Angeles, an area of dense commercial high-rise building development. These results are refined and extended by Davis et al. [this issue].

Item Type:Article
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Hauksson, Egill0000-0002-6834-5051
Additional Information:© 1989 by the American Geophysical Union. Received February 20, 1989; accepted February 22, 1989. We would like to thank Charlie Sammis and Andy Michaels for reviewing this introduction and the authors of the Whittier Narrows Earthquake special section for making preprints of their papers available to us. E. Hauksson was supported by USGS grant 14-08-0001-G1328.
Group:Seismological Laboratory
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Issue or Number:B7
Record Number:CaltechAUTHORS:20130220-082856514
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Official Citation:Hauksson, E., and R. S. Stein (1989), The 1987 Whittier Narrows, California, earthquake: A Metropolitan shock, J. Geophys. Res., 94(B7), 9545–9547, doi:10.1029/JB094iB07p09545
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37008
Deposited By: Tony Diaz
Deposited On:20 Feb 2013 19:16
Last Modified:09 Nov 2021 23:26

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