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Band of precariously balanced rocks between the Elsinore and San Jacinto, California, fault zones: Constraints on ground motion for large earthquakes

2006; Geological Society of America; Volume: 34; Issue: 3 Linguagem: Inglês

10.1130/g22127.1

1943-2682

James N. Brune, Abdolrasool Anooshehpoor, Matthew D. Purvance, Richard J. Brune,

Seismic Waves and Analysis

Research Article| March 01, 2006 Band of precariously balanced rocks between the Elsinore and San Jacinto, California, fault zones: Constraints on ground motion for large earthquakes James N. Brune; James N. Brune 1Seismological Laboratory, University of Nevada, Reno, Nevada 89557, USA Search for other works by this author on: GSW Google Scholar Abdolrasool Anooshehpoor; Abdolrasool Anooshehpoor 1Seismological Laboratory, University of Nevada, Reno, Nevada 89557, USA Search for other works by this author on: GSW Google Scholar Matthew D. Purvance; Matthew D. Purvance 1Seismological Laboratory, University of Nevada, Reno, Nevada 89557, USA Search for other works by this author on: GSW Google Scholar Richard J. Brune Richard J. Brune 23107 Murray Lane, Costa Mesa, California 92626-2735, USA Search for other works by this author on: GSW Google Scholar Geology (2006) 34 (3): 137–140. https://doi.org/10.1130/G22127.1 Article history received: 02 Aug 2005 rev-recd: 25 Oct 2005 accepted: 29 Oct 2005 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation James N. Brune, Abdolrasool Anooshehpoor, Matthew D. Purvance, Richard J. Brune; Band of precariously balanced rocks between the Elsinore and San Jacinto, California, fault zones: Constraints on ground motion for large earthquakes. Geology 2006;; 34 (3): 137–140. doi: https://doi.org/10.1130/G22127.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A spectacular band of precariously and semiprecariously balanced rocks extends from Riverside to near Borrego Valley, California, about halfway between the Elsinore and San Jacinto fault zones. The rocks are distributed in a band a few kilometers wide midway between the San Jacinto and Elsinore fault zones, an indication that the distribution is caused by attenuation of strong ground motion from numerous large events along these two fault zones. These rocks have apparently been in place for thousands of years, and thus place important constraints on ground motions from earthquakes. On the basis of field tests and photographic analysis, the estimated quasi-static toppling accelerations for the precariously balanced rocks are ∼0.32 ± 0.10 g (g = gravitational acceleration). The dynamic toppling accelerations are within this range for earthquakes with waveforms similar to those recorded during the Izmit and Denali earthquakes. These constraints are roughly consistent with the median predicted value of ground motion for M7 earthquakes, but somewhat lower than +1σ ground motion curves, and much lower than the values from the 2% in 50 yr hazard maps. The evidence from these rocks has importance for some of the assumptions that go into calculating probabilistic seismic hazard assessment, including median and standard deviation of ground motion attenuation curves (especially for hard rock, for which few instrumental data are available), the possible existence of random background earthquakes, and the smoothing distance for historical seismicity. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.