scholarly journals Contributed Reports of Widely Felt Earthquakes in California, United States: If They Felt it, Did They Report it?

2021 ◽  
Vol 9 ◽  
Author(s):  
Susan E. Hough
Keyword(s):  
Los Angeles ◽  
Household Income ◽  
Southern California ◽  
Response Rate ◽  
Clear Correlation ◽  
Intensity Data ◽  
First Order ◽  
Average Household Income ◽  
Large Earthquakes ◽  
Zip Code

In a recent study, Hough and Martin (2021) considered the extent to which socioeconomic factors influence the numbers and distribution of contributed reports available to characterize the effects of both historical and recent large earthquakes. In this study I explore the question further, focusing on analysis of widely felt earthquakes near major population centers in northern and southern California since 2002. For most of these earthquakes there is a correlation between average household income in a postal ZIP code and the population-normalized rate of responses to the DYFI system. As past studies have demonstrated, there is also a strong correlation between DYFI participation and the severity of shaking. This first-order correlation can obscure correlations with other factors that influence participation. Focusing on five earthquakes between 2011 and 2021 that generated especially uniform shaking across the greater Los Angeles, California, region, response rate varies by two orders of magnitude across the region, with a clear correlation with demographics, and consistent spatial patterns in response rate for earthquakes 10 years apart. While there is no evidence that uneven DYFI participation in California impacts significantly the reliability of intensity data collected, the results reveal that DYFI participation is significantly higher in affluent parts of southern California compared to economically disadvantaged areas.

scholarly journals A revised position for the primary strand of the Pleistocene-Holocene San Andreas fault in southern California

2021 ◽  
Vol 7 (13) ◽  
pp. eaaz5691
Author(s):  
Kimberly Blisniuk ◽  
Katherine Scharer ◽  
Warren D. Sharp ◽  
Roland Burgmann ◽  
Colin Amos ◽  
...  
Keyword(s):  
Los Angeles ◽  
Southern California ◽  
San Andreas Fault ◽  
Slip Rate ◽  
Large Magnitude ◽  
Slip Rates ◽  
San Andreas ◽  
The Pacific ◽  
Large Earthquakes ◽  
Dependent Probability

The San Andreas fault has the highest calculated time-dependent probability for large-magnitude earthquakes in southern California. However, where the fault is multistranded east of the Los Angeles metropolitan area, it has been uncertain which strand has the fastest slip rate and, therefore, which has the highest probability of a destructive earthquake. Reconstruction of offset Pleistocene-Holocene landforms dated using the uranium-thorium soil carbonate and beryllium-10 surface exposure techniques indicates slip rates of 24.1 ± 3 millimeter per year for the San Andreas fault, with 21.6 ± 2 and 2.5 ± 1 millimeters per year for the Mission Creek and Banning strands, respectively. These data establish the Mission Creek strand as the primary fault bounding the Pacific and North American plates at this latitude and imply that 6 to 9 meters of elastic strain has accumulated along the fault since the most recent surface-rupturing earthquake, highlighting the potential for large earthquakes along this strand.

Predominant seismic source distance and magnitude maps for Los Angeles, Orange, and Ventura Counties, California

1996 ◽  
Vol 86 (5) ◽  
pp. 1645-1649 ◽  
Author(s):  
Chris H. Cramer ◽  
Mark D. Petersen
Keyword(s):  
Los Angeles ◽  
Southern California ◽  
Grid Point ◽  
Seismic Source ◽  
Hazard Map ◽  
San Andreas ◽  
Source Distance ◽  
Seismic Hazard Map ◽  
First Time ◽  
Large Earthquakes

Abstract Hazard deaggregation at each grid point of a probabilistic seismic hazard map can provide maps of the most probable seismic source distance and magnitude. Maps of predominant seismic source distance and magnitude for PGA, and 5% damped spectral acceleration (SA) at 0.3-, 1.0-, and 2.0-sec periods are produced for the first time for Los Angeles, Orange, and Ventura counties in southern California. These maps show that large earthquakes on faults local to any site generally dominate the 10% probability of exceedence in 50- and 100-yr hazards in southern California. Major faults, like the San Andreas, San Jacinto, and Elsinore faults, dominate mainly in their vicinity. At spectral periods beyond 2 sec, earthquakes on these major faults can dominate out to larger distances.

The Sunland Grizzly

2014 ◽  
Vol 91 (4) ◽  
pp. 56-63
Author(s):  
Josh Sides
Keyword(s):  
Los Angeles ◽  
Los Angeles County ◽  
Southern California ◽  
Grizzly Bear ◽  
Science And Art ◽  
Founding Director

In 1916, Cornelius Birket Johnson, a Los Angeles fruit farmer, killed the last known grizzly bear in Southern California and the second-to last confirmed grizzly bear in the entire state of California. Johnson was neither a sportsman nor a glory hound; he simply hunted down the animal that had been trampling through his orchard for three nights in a row, feasting on his grape harvest and leaving big enough tracks to make him worry for the safety of his wife and two young daughters. That Johnson’s quarry was a grizzly bear made his pastoral life in Big Tujunga Canyon suddenly very complicated. It also precipitated a quagmire involving a violent Scottish taxidermist, a noted California zoologist, Los Angeles museum administrators, and the pioneering mammalogist and Smithsonian curator Clinton Hart Merriam. As Frank S. Daggett, the founding director of the Los Angeles County Museum of History, Science and Art, wrote in the midst of the controversy: “I do not recollect ever meeting a case where scientists, crooks, and laymen were so inextricably mingled.” The extermination of a species, it turned out, could bring out the worst in people.

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