Heterogeneous rupture in the great Cascadia earthquake of 1700 inferred from coastal subsidence estimates
Engelhart, Simon E.
Hawkes, Andrea D.
Horton, Benjamin P.
Nelson, Alan R.
Witter, Robert C.
MetadataShow full item record
KeywordMegathrust earthquake; Cascadia; Paleoseismology; Coastal subsidence; Earthquake deformation; Microfossils
Past earthquake rupture models used to explain paleoseismic estimates of coastal subsidence during the great A.D. 1700 Cascadia earthquake have assumed a uniform slip distribution along the megathrust. Here we infer heterogeneous slip for the Cascadia margin in A.D. 1700 that is analogous to slip distributions during instrumentally recorded great subduction earthquakes worldwide. The assumption of uniform distribution in previous rupture models was due partly to the large uncertainties of then available paleoseismic data used to constrain the models. In this work, we use more precise estimates of subsidence in 1700 from detailed tidal microfossil studies. We develop a 3-D elastic dislocation model that allows the slip to vary both along strike and in the dip direction. Despite uncertainties in the updip and downdip slip extensions, the more precise subsidence estimates are best explained by a model with along-strike slip heterogeneity, with multiple patches of high-moment release separated by areas of low-moment release. For example, in A.D. 1700, there was very little slip near Alsea Bay, Oregon (~44.4°N), an area that coincides with a segment boundary previously suggested on the basis of gravity anomalies. A probable subducting seamount in this area may be responsible for impeding rupture during great earthquakes. Our results highlight the need for more precise, high-quality estimates of subsidence or uplift during prehistoric earthquakes from the coasts of southern British Columbia, northern Washington (north of 47°N), southernmost Oregon, and northern California (south of 43°N), where slip distributions of prehistoric earthquakes are poorly constrained.
Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 118 (2013): 2460–2473, doi:10.1002/jgrb.50101.
Showing items related by title, author, creator and subject.
Toomey, Douglas R.; Allen, Richard M.; Barclay, Andrew H.; Bell, Samuel W.; Bromirski, Peter D.; Carlson, Richard L.; Chen, Xiaowei; Collins, John A.; Dziak, Robert P.; Evers, Brent; Forsyth, Donald W.; Gerstoft, Peter; Hooft, Emilie E. E.; Livelybrooks, Dean; Lodewyk, Jessica A.; Luther, Douglas S.; McGuire, Jeffrey J.; Schwartz, Susan Y.; Tolstoy, Maya; Trehu, Anne M.; Weirathmueller, Michelle; Wilcock, William S. D. (The Oceanography Society, 2014-06)Increasing public awareness that the Cascadia subduction zone in the Pacific Northwest is capable of great earthquakes (magnitude 9 and greater) motivates the Cascadia Initiative, an ambitious onshore/offshore seismic and ...
Segmentation of plate coupling, fate of subduction fluids, and modes of arc magmatism in Cascadia, inferred from magnetotelluric resistivity Wannamaker, Philip E.; Evans, Rob L.; Bedrosian, Paul A.; Unsworth, Martyn J.; Maris, Virginie; McGary, R Shane (John Wiley & Sons, 2014-11-11)Five magnetotelluric (MT) profiles have been acquired across the Cascadia subduction system and transformed using 2-D and 3-D nonlinear inversion to yield electrical resistivity cross sections to depths of ∼200 km. Distinct ...
A 2-D tomographic model of the Juan de Fuca plate from accretion at axial seamount to subduction at the Cascadia margin from an active source ocean bottom seismometer survey Horning, Greg W.; Canales, J. Pablo; Carbotte, Suzanne M.; Han, Shuoshuo; Carton, Hélène; Nedimovic, Mladen R.; van Keken, Peter E. (John Wiley & Sons, 2016-08-14)We report results from a wide-angle controlled source seismic experiment across the Juan de Fuca plate designed to investigate the evolution of the plate from accretion at the Juan de Fuca ridge to subduction at the Cascadia ...