{"id":9580,"date":"2020-06-27T23:11:52","date_gmt":"2020-06-28T07:11:52","guid":{"rendered":"http:\/\/earthjay.com\/?p=9580"},"modified":"2023-06-25T18:54:55","modified_gmt":"2023-06-25T18:54:55","slug":"earthquake-report-owens-valley-ca","status":"publish","type":"post","link":"https:\/\/earthjay.com\/?p=9580","title":{"rendered":"Earthquake Report: Owens Valley, CA"},"content":{"rendered":"

Well, the east side of the Sierra lives up to its reputation for being in earthquake country. From the July 2019 Ridgecrest Earthquake Sequence (reports here<\/a>)to some shakers east of Mono Lake, to the May 2020 Monte Cristo Earthquake Sequence (report here<\/a>) to some earthquakes in the Owens Lake area of California. Residents of Olancha, Lone Pine, and Keeler felt strong shaking from a magnitude M 5.8 earthquake, also preceded by about 2 days with a M 4.6 temblor.<\/p>\n

https:\/\/earthquake.usgs.gov\/earthquakes\/eventpage\/ci39493944\/executive<\/a><\/p>\n

The plate tectonics in the western US is overwhelmingly dominated by the plate boundary between the North America and Pacific plate. The North America plate moves south “relative” to the Pacific plate. Standing on the Pacific plate, looking across the fault, the North America plate moves to your right (a right-lateral strike-slip fault).<\/p>\n

Here, both plates are moving “absolutely” in the northwestern direction, but the Pacific plate is moving slower. Therefore the relative sense of motion results in a right-lateral fault.<\/p>\n

The plates move side-by-side at a velocity (speed) of about 50 mm per year (2 inches per year). In California, most of this relative motion is localized along the San Andreas fault system. But there are sub-parallel “sibling” faults that also share some of the “slip budget” (their proportion of the 50 mm\/yr).<\/p>\n

About 20% of the relative plate motion is found along faults on the east side of the Sierra Nevada, along the Eastern California Shear Zone and the Walker Lane system.<\/p>\n

Further to the north, in northern California, Oregon, Washington, and Canada, the relative plate motion is compressive, forming the Cascadia subduction zone<\/a>.<\/p>\n

East of California, the plate boundary experiences relative extension, forming the geomorphic province called the Basin and Range<\/a>. The faults in the Basin and Range are mostly normal faults (extensional faults).
\nRead more about the different fault types here<\/a>.<\/p>\n

On 26 March 1872 there was a large earthquake that ruptured faults from south of Owens Lake near Olancha, CA northwards to Big Pine, CA. This earthquake may be the largest historic earthquake in California with a magnitude of M 7.8 to 7.9 (Hough and Hutton, 2008).<\/p>\n

This earthquake was the result of slip on the Owens Valley fault system (OVF). The majority of slip was right-lateral strike-slip, but because the OVF is not perfectly aligned with the relative plate motion, some of the slip on these faults was normal slip (i.e. extensional).<\/p>\n

There are still preserved remains of structures damaged by the earthquake in Lone Pine, CA.<\/p>\n

The OVF has been mapped and trenched across to learn about the prehistoric record of earthquakes on the fault.<\/p>\n

Also, from measurements of features that have been offset along the fault during earthquakes, along with knowledge of the age of those features, we can estimate how fast the frust is moving relatively across the fault. Below are some figures that help us learn about this historty and activity of the OVF (e.g. Bacon and Pezzopane, 2007; Kirby et al, 2008; Haddon et al., 2013; Bacon et al., 2019).<\/p>\n

Beth Haddon et al. (2013) conducted a very interesting study that compiled and updated previous slip estimates for the 1872 OVF earthquake. Their analysis vastly improved the estimate of how much the fault slipped at different locations along the fault (i.e. the fault slip distribution) and included a novel way to account for uncertainty (a.k.a. error) in the measurements of these offsets.<\/p>\n

California Geological Survey Engineering Geologist Brian Olson was sent to the field to make observations of fault rupture, landslides, and liquefaction related to this earthquake. Some of his tweets from the field are included below in the social media section.<\/p>\n

Below is my interpretive poster for this earthquake<\/font><\/h2>\n