LiDAR and field observations of slip distribution for the most recent surface ruptures along the central San Jacinto fault

Bulletin of the Seismological Society of America
By: , and 

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Abstract

We measured offsets on tectonically displaced geomorphic features along 80 km of the Clark strand of the San Jacinto fault (SJF) to estimate slip‐per‐event for the past several surface ruptures. We identify 168 offset features from which we make over 490 measurements using B4 light detection and ranging (LiDAR) imagery and field observations. Our results suggest that LiDAR technology is an exemplary supplement to traditional field methods in slip‐per‐event studies. Displacement estimates indicate that the most recent surface‐rupturing event (MRE) produced an average of 2.5–2.9 m of right‐lateral slip with maximum slip of nearly 4 m at Anza, a Mw 7.2–7.5 earthquake. Average multiple‐event offsets for the same 80 kms are ∼5.5  m, with maximum values of 3 m at Anza for the penultimate event. Cumulative displacements of 9–10 m through Anza suggest the third event was also similar in size. Paleoseismic work at Hog Lake dates the most recent surface rupture event at ca. 1790. A poorly located, large earthquake occurred in southern California on 22 November 1800; we relocate this event to the Clark fault based on the MRE at Hog Lake. We also recognize the occurrence of a younger rupture along ∼15–20  km of the fault in Blackburn Canyon with ∼1.25  m of average displacement. We attribute these offsets to the 21 April 1918 Mw 6.9 event. These data argue that much or all of the Clark fault, and possibly also the Casa Loma fault, fail together in large earthquakes, but that shorter sections may fail in smaller events.

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Publication type Article
Publication Subtype Journal Article
Title LiDAR and field observations of slip distribution for the most recent surface ruptures along the central San Jacinto fault
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120110068
Volume 102
Issue 2
Year Published 2012
Language English
Publisher Seismological Society of America
Publisher location Stanford, CA
Contributing office(s) Earthquake Science Center
Description 22 p.
First page 598
Last page 619
Country United States
State California
Online Only (Y/N) N
Additional Online Files (Y/N) N
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