Eastern California Shear Zone

The Eastern California Shear Zone or ECSZ is a “swatch of individual [earthquake] faults” according to Berkeley Seimology Lab. The zone runs from “the northern Owens Valley [to] east of the Sierra Nevada [and then to] the Mojave Desert [and] all the way to the Palm Springs area…” in the south. It is a vast area of earthquake activity.

The ECSZ is a relatively unknown earthquake hazard area with a past history of numerous signficant historical quakes and earthquake swarms. The ECSZ is located in South Eastern California and is expansive including the mojave desert and numerous towns including: Lone Pine, Bishop, and Ridgecrest.

ECSZ Historically Significant Earthquakes:

The ECSZ has seen significant historical earthquakes both in recent times and long ago. The 1995 Ridgecrest Earthquake Sequnce was a most signficant one, as well as the Ridgecrest Quake Sequence of 2019. This 2019 ECSZ sequence saw a magnitude quake of 7.1.

In 1872 there was an incredible quake in Owens Valley near the present day town of Lone Pine. It had an estimated range of 7.4 to 7.9 in magnitude and is considered an X on the mercali scale. This is one of the largest earthquakes in California modern times.

Those are just some of the past quakes and there are literally thousands more.

About the Eastern California Shear Zone [ECSZ]:

The Eastern California Shear Zone “is thought to accommodate nearly a quarter of relative plate motion between the Pacific and North America plates” according to a paper by the Geological Society of America, 2008. The ECSZ “is an ideal natural laboratory in which to study the spatial and temporal evolution of active plate boundary fault systems.”

The Zone is “an evolving component” of the Plate Boundary system. And “in the Mojave Desert…the eastern California shear zone comprises a 100-km-wide network of NNW–trending right-lateral faults.” There are numerous faults in the area. The ECSZ “accommodates the majority of Pacific–North America plate boundary motion east of the San Andreas fault.”

The area of the zone include: the Mojave Desert, Owens Valley, and Fishlake Valley area.

Source: Active Techtonics of the eastern California Shear Zone, by Frankel, Glazner, Kirby, Monastero, Strane, Oskin, Unruh, Walker, Anandakrishnan, Bartley, Coleman, Dolan,Finkel, Greene, Kylander-Clark, Marrero, Owen, and Phillips.

About Sheer Zones:

Sheer Zones are “zones of intense ductile deformation that are thin relative their lateral extent.” Sheer zones are similar to faults in that “they lack through-going brittle fractures.” But – They are similar to faults in that “typically show offsets of older structures.” The two are related though. Open Education Alberta.

Wikipedia defines a sheer zone as “a thin zone within the Earths Crust or Upper Mantle that has been strongly deformed…” The definition explains that this happens “due to the walls of rock on either side of the zone slipping past each other…” Source Wiki. By some definitions there about three different types of sheer zones.

In the world of Earthquakes and Earthquake Insurance – Faults and Sheer Zones are both similarly important.

How the Eastern California Shear Zone Got its Name:

Simple. The ECSZ or Eastern California Shear Zone got its name by combining the location with the name of a geological zone. Location + Geological Zone. Eastern California is the Location or Area and the Shear Zone is the name of the deformed crust or upper mantle. Put them togehter and you get the name Eastern California Sheer Zone.

In theory a slightly more fitting name might be the South Eastern California Shear Zone or SECSZ. That of course is our opinion.

Where is Eastern California:

Eastern California is obviously on the eastern half of the state. Looking at a typical map of the state it is the right hand side. Most of the eastern portion of the state of California exists though, in the South. This is easier to understand while staring at a map of the state. This is due to the fact that California runs along a jagged diagnal to the lower right corner of most maps. Typically when individuals are referring to Eastern California they are referring to South Eastern California. South Eastern California is bordered by Arizona to the east, Nevada to the north, Western/ Central California to the west and Mexico to the south.

Eastern California is made up of mostly desert and mountain zones. It is considered an arid environment and has a very low population.

Please note that the ECSZ area borders are not the exact same as the Eastern California borders. This is because Eastern California is based on political maps and the Eastern California Sheer Zone is based on geolocial maps.

Some of the Faults in the ECSZ:

Some of the faults in the Eastern California Sheer Zone include:

Ash Hill fault

Airport Lake fault

Blackwater fault

Bicycle Lake fault

Cady fault

Coyote Lake fault

Camp Rock fault

Deep Springs fault

Death Valley–Fish Lake Valley fault

Emigrant Peak fault

Fort Irwin fault

Garlock fault

Goldstone Lake fault

Helendale fault

Harper Lake fault

Saline Valley fault

Lenwood fault
Lavic Lake fault

Lockhart fault

Ludlow fault

Manix fault
Owens Valley fault

Pisgah fault

Panamint Valley

Panamint Valley fault
Southern Death Valley fault

Stateline fault

Sierra Nevada frontal fault

Tiefort Mountain fault

Tin Mountain fault

Towne Pass fault

White Mountains fault

The ECSZ Mapping Project:

The Eastern California Shear Zone is active enough to have its own “Mapping Project” – The Eastern California Shear Zone Mapping Project. The project is funded by the National Cooperative Geologic Mapping Program. Information about this program can be found on the USGS site here.

The project attempts to address the following considerations:

-“What are the timing and spatial distribution of fault slip across the northern portion of the ECSZ, and how do faults interact with one another, particularly at fault intersections? “

-“What is the imprint of early Mesozoic compression and Cenozoic extension on the Quaternary and active tectonics of the region? What are the distribution and geometry of groundwater basins in the northern Mojave Desert, what are the tectonic controls, and how do they fit into the context of the ECSZ?” 

-“What are the characteristics of contemporaneous Quaternary depositional units between the northern Mojave Desert and the Lower Colorado River Corridor? “

The ECSZ Mapping Project is an important tool created to learn more about this vital earth movement zone.

Earthquake Insurance in the Eastern California Sheer Zone:

Can you get earthquake insurance in eastern California? Yes, many consumers are eligible to procure earthquake policies in this region. The CEA and other independent quake providers provide options. Inquire with a licensed agent.

Other Sources of Information Berkeley EDU, Wikipedia, USGS, among others.