Coastal uplift associated with the 1992 Cape Mendocino earthquake, northern California

By: , and 



The April 25,1992, Cape Mendocino earthquake (Ms 7.1) uplifted ∼24 km of the northern California coast at the southern end of the Cascadia subduction zone, uplift which resulted in coastal emergence that caused extensive mortality of intertidal organisms between Cape Men docino and Punta Gorda. We estimated the amount of uplift by measuring the vertical extent of mortality of 14 sessile intertidal species on rocky sections of shore. The uplift profile along the coast is generally parallel to the strike of the earthquake focal mechanism and forms a broad, flat-topped arch ∼24 km long with a gentle south limb and a steeper north limb. The maximum uplift of 1.4 ±0.2 m is near the center of the profile. The profile is a manifestation of the more widespread domal upwarp produced by slip on an east-dipping buried thrust fault along or near the Cascadia megathrust. Small, new emergent terraces have formed where wave-cut intertidal platforms have been elevated. The new terraces resemble raised late Holocene benches that probably record paleoearthquakes similar to the 1992 event. However, several of the late Holocene terraces are broader and more continuous. These terraces, which extend several tens of kilometres north and south of the 1992 uplift, suggest that some paleoearthquakes were much larger than magnitude 7.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Coastal uplift associated with the 1992 Cape Mendocino earthquake, northern California
Series title Geology
DOI 10.1130/0091-7613(1994)​022<0195:CUAWTC>​2.3.CO;2
Volume 22
Issue 3
Year Published 1994
Language English
Publisher Geological Society of America
Description 4 p.
First page 195
Last page 198
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