Stanford scientists use ‘virtual earthquakes’ to forecast Los Angeles quake

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[MUSIC] Stanford University.>>This study was motivated by super
computer simulations that showed that the, the
structure of the Earth’s crust in Southern California,
would act to shape the basin stronger than we had
previously anticipated. In order to test that simulation, what we
did was develop a new approach, which we call the
virtual earthquake approach. Now, the virtual earthquake approach uses
what we call the ambient seismic field which are the waves that are present in
the Earth at all times. They are coursing under us right now. They’re generated by the action of ocean
waves.>>And those waves, because they have
different pressure then, they transfer to the sea
bottom. And these get transmitted to the crust where we actually have instruments record
it.>>Those waves, even though they’re billions of times weaker than earthquake
waves. They interact with the complex geologic
structure of the crust in just the same way. In this instance, what it shows is that, seismic waves travel from the San Andreas
Fault. Which is located to the east and to the
north of Los Angeles. Through what we call a wave guide. So this is a, a series of shallow
sedimentary basins.>>Those waveguides and the basin have,
they are basically surrounded by mountains, and mountains deposit a lot
of sediments, with erosion. And those sediments are not compacted. It’s like sand on the beach. So they are very compliant, so they can
move more easily.>>The waves travel through that corridor
towards Los Angeles. And are essentially guided into the sedimentary basin that underlies Los
Angeles. Once they’re in that basin, they
reverberate, they get amplified, and they cause stronger shaking
than would otherwise occur. We have to do something about. [INAUDIBLE] It’s a new way of testing
these sort of simulations. And that’s the information that we use to
characterize. The hazard that say Los Angeles faces, and
also, that’s the information the engineers use
to design structures. There are other cities that, that lie on
sedimentary basins, cities like Seattle, parts of the San
Francisco Bay area, Tokyo Mexico City is a classic case, all
of these cities are earthquake threatened, and all
of them have this. Extra threat because of this space and
amplification.>>So, the, the sort of work that we’ve
pioneered in Southern California, could be applied in
many other parts of the world. [INAUDIBLE].>>For more, please visit us at
stanford.edu.

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