Large active seafloor faults offshore California may produce earthquakes and tsunamis

What is it about?

We examine two of the largest active fault zones offshore southern California to understand their geologic history and estimate the possibility of large earthquakes, seafloor deformation, and resulting tsunamis that may affect the populous California coast. Two moderate earthquakes (M~6) occurred during the 1980s which provide information on the depth of active faulting which is needed to estimate the largest magnitude earthquakes that may occur on these faults. Technology used by oil companies was used in this study to image the faults and geology below the seafloor, and technology used by the government to map the seafloor topography (bathymetry) was used to map the length, width and character of seafloor deformation -uplift and sinking- that may produce tsunamis

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Why is it important?

Active faulting beneath ocean may produce large earthquakes that can damage important structures along the adjacent coast including ports, harbors, bridges, power plants, military installations, and housing developments. The added threat of flooding by tsunami inundation may occur even though faults farther from shore may not generate strong shaking on the coast, but tsunamis can propagate 100s to 1000s of miles producing destruction to vulnerable low-lying coastal areas. Major infrastructure such as nuclear power plants including waste storage facilities may be susceptible to such large events, so that adequate protection may be designed and constructed for such facilities. Major ports and harbors need to know what threats may arise from large offshore earthquakes and tsunamis so that emergency preparedness planning, design, and construction may occur. In addition, the southern California coast is very popular for residents and tourists alike so that emergency planners can provide warning to coastal visitors should a large earthquake and possible tsunami occur.

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