Location and size of the 1927 Lompoc, California, earthquake from tsunami data

Abstract The Lompoc earthquake of 4 November 1927 ( M s 7.0) was one of the largest offshore events in California, and the associated tsunami was recorded in Hawaii as well as on the California coast. The epicenter of this event has long been debated; one location is offshore where the ocean is about 1000-m deep, whereas another location is very near shore beneath a water depth of less than 100 m. We analyzed the tsunami records from this event. From tsunami travel times, the source location was estimated to be well offshore at about 34.2°N, 120.75°W, consistent with recent seismic waveform analysis. Waveform modeling of the tsunami also supports an outer continental shelf location. The seismic moment is estimated to be 3 × 10 26 dyne · cm, corresponding to a moment magnitude of 7.0. The tsunami computation reproduced the large tsunami in Hawaii, indicating that the observed large tsunami was due to bathymetry effects, particularly near Hilo Bay. The tsunami magnitude of 7.6 obtained from the Hawaiian recordings by Abe thus appears to be an overestimate.