Los-Angeles

Los-Angeles

Geologists studying the Jan. 12 Haiti earthquake say the risk of destructive tsunamis is higher than expected in places such as Kingston, Istanbul, and Los Angeles. Like Haiti’s capital, these cities all lie near the coast and near an active geologic feature called a strike-slip fault where two tectonic plates slide past each other like two hands rubbing against each other.

Until now, geologists did not consider the tsunami risk to be very high in these places because when these faults rupture, they usually do not vertically displace the seafloor much, which is how most tsunamis are generated. This latest research suggests even a moderate earthquake on a strike-slip fault can generate tsunamis through submarine landslides, raising the overall tsunami risk in these places.

“The scary part about that is you do not need a large earthquake to trigger a large tsunami,” said Matt Hornbach, research associate at The University of Texas at Austin’s Institute for Geophysics and lead author on a paper describing the research in the Oct. 10 online edition of the journal Nature Geoscience.

“Organizations that issue tsunami warnings usually look for large earthquakes on thrust faults,” said Hornbach. “Now we see you don’t necessarily need those things. A moderate earthquake on a strike-slip fault can still be cause for alarm.”

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