7.23 Mass-Movement Causes: Earthquakes

Abstract

Earthquakes can trigger all types of landslides, and triggered landslides contribute significantly to landscape morphology and lowering in tectonically active areas. The most abundant types of landslides triggered in earthquakes are fairly shallow, disrupted falls and slides in rock and soil; larger, deeper landslides are less common but contribute significantly to total landslide volumes. Studies of worldwide earthquakes have allowed characterization of the relation between earthquake magnitude and (1) maximum landslide distance; (2) areas in which landslides occur; (3) total number of landslides triggered; (4) total, maximum, and average areas of landslides; and (5) total, maximum, and average landslide volumes. Regional studies indicate that earthquake-triggered landslides contribute significantly to landscape lowering, commonly comparable to the contributions from other erosive processes. Near active subduction zones, landscape lowering from earthquake-triggered landslides can range from 0.2 to 7mmyr−1; near strike-slip plate boundaries, the range is 0.02–0.2mmyr−1. Thus, earthquake-triggered landsliding is a significant geomorphic process that both shapes and lowers landscapes in tectonically active areas.