Faulting, damage, and intensity in the Canyondam earthquake of May 23, 2013

Open-File Report 2016-1145
By: , and 



On Thursday evening, May 23, 2013 (0347 May 24 UTC), a moment magnitude (Mw) = 5.7 earthquake occurred northeast of Canyondam, California. A two-person team of U.S. Geological Survey scientists went to the area to search for surface rupture and to canvass damage in the communities around Lake Almanor. While the causative fault had not been identified at the time of the field survey, surface rupture was expected to have occurred just south of Lake Almanor, approximately 2–4 kilometers south of the epicenter. No surface rupture was discovered. Felt intensity among the communities around Lake Almanor appeared to vary significantly. Lake Almanor West (LAW), Lake Almanor Country Club (LACC), and Hamilton Branch (HB) experienced Modified Mercalli Intensity (MMI) ≥7, whereas other communities around the lake experienced MMI ≤6; the maximum observed intensity was MMI 8, in LAW. Damage in the high intensity areas consisted of broken and collapsed chimneys, ruptured pipes, and some damage to foundations and to structural elements within houses. Although this shaking damage is not usually expected for an Mw 5.7 earthquake, the intensities at Lake Almanor Country Club correlate with the peak ground acceleration (38 percent g) and peak ground velocity (30 centimeters per second) recorded by the California Strong Motion Instrumentation Program accelerometer located at the nearby Lake Almanor Fire Station. The intensity distribution for the three hardest hit areas (LAW, LACC, and HB) appears to increase as the azimuth from epicenter to the intensity sites approaches the fault strike. The small communities of Almanor and Prattville on the southwestern shore of Lake Almanor experienced somewhat lower intensities. The town of Canyondam experienced a lower intensity as well, despite its location up-dip of the earthquake rupture. This report contains information on the earthquake itself, the search for surface rupture, and the damage we observed and compiled from other sources. 

Suggested Citation

Chapman, K., Gold, M.B., Boatwright, J., Sipe, J., Quitoriano, V., Dreger, D., and Hardebeck, J., 2016, Faulting, damage, and intensity in the Canyondam earthquake of May 23, 2013: U.S. Geological Survey Open-File Report 2016-1145, 49 p., http://dx.doi.org/10.3133/ofr20161145.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Regional Seismicity
  • Regional Geology and Tectonics
  • Earthquake Mechanism, Fault, and Rupture Extent
  • Search for Surface Rupture
  • Postearthquake Damage Assessment
  • Isoseismal Distribution
  • Conclusions
  • References Cited
  • Appendix 1. Intensity Sites
  • Appendix 2. Damage Photographs

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Faulting, damage, and intensity in the Canyondam earthquake of May 23, 2013
Series title Open-File Report
Series number 2016-1145
DOI 10.3133/ofr20161145
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description iv, 49 p.
Country United States
State California
Online Only (Y/N) Y