Geology of California

California lies at the convergence of two tectonic plates–the North American plate and the Pacific plate–which come together near the coast to create a shifting fault line that is the cause of many earthquakes.

The following is from an interview with Dr. Linda Reinen, Associate Professor of Geology at Pomona College:

“The two sections of the San Andreas Fault that cut through Southern California have a history of very large earthquakes (> Magnitude 7.7). These sections ruptured in 1858 and 1680, respectively, and each section is expected to produce large earthquakes approximately every 150 years. Thus, the San Andreas Fault in Southern California is overdue for the next large earthquake.

The intensity and duration of shaking depends on proximity to the fault and the geology of the region. Intense shaking occurs in areas close to the fault, and sediment-filled basins shake longer and harder than bedrock regions at a similar distance from the fault. Thus the Coachella Valley, Los Angeles Basin, Santa Clara River Valley and Oxnard Plain all would experience intense shaking for a long time (up to 2 minutes in the Coachella Valley) in this particular scenario. To help put this in perspective, the damage from the 1994 M6.7 Northridge earthquake occurred during 7-15 seconds of shaking” (L. Reinen, personal communication, December 3, 2014).

Environmental Justice and Natural Disasters

• “Environmental Justice is the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. EPA has this goal for all communities and persons across this Nation. It will be achieved when everyone enjoys the same degree of protection from environmental and health hazards and equal access to the decision-making process to have a healthy environment in which to live, learn, and work.” –United States Environmental Protection Agency

• A natural extreme event becomes a hazard or “disaster” only when it interacts with a human population, exposing a portion of the population to the forces of the event (Rodrigue, 1993)

• Natural hazards disproportionately devastate the poor because social mechanisms of recovery respond more slowly to poorer areas than they do to prosperous ones (Susman et al., 1983)

• Socially marginalized areas (low-income communities and/or communities of color): 1) suffer from greater infrastructural instability; 2) have less robust emergency preparedness plans; 3) receive less (or less immediate) aid for emergency response and/or long-term recovery; and 4) enjoy less attention from the media during times of natural disaster

Loma Prieta Earthquake of 1989

The 1989 Loma Prieta quake, which emphasized the suffering of the affluent Marina District of San Francisco sixty miles from the epicenter, had very little coverage of the distress caused in the largely African-American Oakland equidistant from the epicenter (Lee & Solomon, 1991; Smith, 1992). Conspicuously ignored was the catastrophic damage experienced in the largely Latino Watsonville and in the countercultural college town, Santa Cruz–both of which were much closer to the epicenter. Some of this disparity in coverage has to do with the spatial and social orientation of the media, as the region’s major newspapers are based in San Francisco rather than in the smaller communities outside the Bay Area.

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Click the following link to see a map of the magnitude of the Loma Prieta quake:

http://earthquake.usgs.gov/earthquakes/shakemap/nc/shake/LomaPrieta/

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Explore the following links to view photos of the damage experienced as a result of the Loma Prieta quake:

http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=13&t=101634&s=0&d=2&d=22

http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=13&t=101634&s=0&d=2&d=22

http://www.ngdc.noaa.gov/hazardimages/event/show/14

Which areas are most clearly and frequently depicted in the photos above? Why?

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What can you tell about the impacts of the Loma Prieta earthquake from the following pairs of maps?

ShakeMap and Median Household Income

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ShakeMap and White Census Population

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ShakeMap and Hispanic Census Population

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ShakeMap and Black Census Population

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ShakeMap and Asian Census Population

Northridge Earthquake of 1994

Contrary to popular belief, the 1994 Northridge earthquake epicenter occurred in Reseda, a neighborhood in north-central Los Angeles. The media covered Northridge, which is a much more upscaled area than Reseda. It has a per capita income of $23,308, while Reseda has a per capita income of $15,177. For comparison, the average per capita income of California is $16,409 (US Census, 1990). Also important to note is the media’s failure to cover the hardest-hit ZIP code in the city  (90016); this ZIP code is located in the largely African-American Crenshaw District, which suffered the greatest concentration of destroyed and heavily damaged buildings in the city. Furthermore, average per capita income in communities extensively covered by the media was $26,069, while average per capita income in communities minimally covered by the media was only $14,145 (Rodrigue et al., 1997).

Very disturbingly, there proved to be an association between media attention–itself skewed by ethnicity, race, and income–and rates of recovery (Rodrigue et al., 1997).

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Click on the following link to see a map of the magnitude of the Northridge quake:

http://earthquake.usgs.gov/earthquakes/shakemap/sc/shake/Northridge/download/intensity.jpg

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Explore the following links to view photos of the damage experienced as a result of the Northridge quake:

http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=19&t=101634&s=0&d=2&d=22

http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=18&t=101634&s=0&d=2&d=22

http://www.ngdc.noaa.gov/hazardimages/event/show/18

Which areas are most clearly and frequently depicted in the photos above? Why?

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What can you tell about the impacts of the Northridge earthquake from the following pairs of maps?

ShakeMap and Median Household Income

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ShakeMap and White Census Population

 

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ShakeMap and Hispanic Census Population

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ShakeMap and Black Census Population

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ShakeMap and Asian Census Population

California ShakeOut Scenario

In 2008, the U.S. Geological Survey produced a report illustrating the potential impacts of a “ShakeOut Scenario,” a large-scale earthquake for which California is long overdue.

Click the following link to view the USGS interactive ShakeOut website: http://www.shakeout.org/california/scenario/.

This website represents one possible realistic earthquake scenario that could take place in Southern California, and provides Southern California residents with ideas about what sort of action they can take now to reduce losses if/when the quake strikes (L. Reinen, personal communication, December 3, 2014).

In an interview with Dr. Linda Reinen, Associate Professor of Geology at Pomona College, she gave the following insight into what California should expect as a result of the ShakeOut:

Dr. Reinen highlighted A USGS report which gives the following information:

•  A major earthquake in Southern California is inevitable and it will be a regional disaster
•  Thousands of square miles will suffer heavy shaking
•  Tens of thousands of people will be injured

          ~1,800 deaths (low due to strong building codes)

          ~95% of rescues are carried out by fellow victims

•  Hundreds of thousands of buildings will be damaged
•  Millions of lives and businesses will be disrupted

In the ShakeOut Scenario, communities located along fault lines and adjacent basins will be heavily affected, making this a regional disaster rather than a local disaster, as Northridge and Loma Prieta were. The implications of a regional-scale disaster like this are that neighboring communities cannot come to the aid of the affected communities by providing emergency response efforts, as they will be recovering from the damage themselves and directing whatever resources they have to their own communities.

Given the results of the 1989 Loma Prieta and 1994 Northridge earthquakes, do you think the ShakeOut Scenario could have differential impacts on particular communties? What kind?

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“Preliminary quake map shows fault lines under schools, hotels, homes”

LA Times, May 6 2014

http://www.latimes.com/local/earthquakes/la-me-adv-fault-map-20140506-story.html#page=1

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Helpful Resources on Earthquake Preparedness:

http://www.earthquakecountry.info/roots/

http://www.redcross.org/prepare/location/home-family/get-kit

Click to access m4240216_Earthquake.pdf

http://www.fema.gov/earthquake

http://www.earthquakeauthority.com/CEAindex.aspx

Resources

Mortensen, Carl E. (1994a). Associate Chief, Branch of Earthquake Geology and Geophysics, US Geological Survey, Menlo Park, CA. Personal communications (March and April).

Mortensen, Carl E. (1994b). Dynamics of the January 17 earthquake. Presentation to the Los Angeles Quake: Event Dynamics, Response, and Reconstruction special session, Hazards Specialty Group, Association of American Geographers, San Francisco (2 April).

White, Gilbert F. and Haas, J. Eugene. (1975). Assessment of research on natural hazards. Cambridge, MA, and London: The MIT Press.

Rodrigue, Christine M., Rovai, Eugenie, and Place, Susan E. (1997). Construction of the “Northridge” Earthquake in Los Angeles’ English and Spanish Print Media:  Damage, Attention, and Skewed Recovery. Nature’s Workshop: Environmental Change in 20th Century Southern California.

Place, Susan E. and Rodrigue, Christine M. (1994). Media Construction of “Northridge earthquake in English and Spanish Print Media in Los Angeles.Nature’s Workshop: Environmental Change in 20th Century Southern California.

Rodrigue, Christine M. (1993). Home with a View: Chaparral Fire Hazard and the Social Geographies of Risk and Vulnerability. The California Geographer 33:105-168.

Susman, Paul, O’Keefe, Phil, and Wisner, Ben. (1983). Global Disasters, a Radical Interpretation. In Interpretations of Calamity, ed. Kenneth Hewitt, 263-283. Boston, MA: Allen and Unwin.

Rosenblum, Gary. (2012). Valley Voice: Earthquake alert system may save lives in our valley. The Desert Sun. (http://www.mydesert.com/article/20121018/OPINION04/310180010/Valley-Voice-Earthquake-alert-system-may-save-lives)

ShakeMaps:

Northridge ShakeMap. 2009. USGS. http://earthquake.usgs.gov/earthquakes/shakemap/sc/shake/Northridge/

Loma Prieta ShakeMap. 2009. USGS.

http://earthquake.usgs.gov/earthquakes/shakemap/nc/shake/LomaPrieta/

GIS Map Data:

Vasquez, Kelvin and Frias-Rodriquez, Miquel. 2013. California City Point Shapefile. United States Census Bureau. http://scec.usc.edu/internships/useit/content/california-cities-point-shapefile

Greenwood, Rebecca and Jara, Marianne. 2012. California Counties Shapefile. http://scec.usc.edu/internships/useit/content/california-counties-shapefiles

Census Data (Socio). 2010. United States Census. https://www.census.gov/geo/maps-data/data/tiger-line.html

Census Data (Economic). 2007-2011. United States Census. https://www.census.gov/geo/maps-data/data/tiger-data.html

Northridge Photos: http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=19&t=101634&s=0&d=2&d=22, http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=18&t=101634&s=0&d=2&d=22,

http://www.ngdc.noaa.gov/hazardimages/event/show/18

Loma Prieta Photos: http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=13&t=101634&s=0&d=2&d=22, http://www.ngdc.noaa.gov/nndc/struts/results?eq_1=13&t=101634&s=0&d=2&d=22,

http://www.ngdc.noaa.gov/hazardimages/event/show/14