Will tsunamis affect California?

Why don't tsunamis hit California?

• Aren't tsunamis caused by underwater earthquakes? Isn't California, a coastal state, on the fault line? Or is the fault line not far enough?

• Answer:

  The San Andreas fault in California is a "strike-slip" fault that, while geologically very active, tends not to create tsunamis. Earthquakes in subduction zones are what cause tsunamis. A subduction zone in a fault is where one tectonic plate is sliding underneath another plate. Subduction zones are prone to "megathrust" earthquakes. Megathrust earthquakes tend to be large and release their energy upward and cause the overriding plate to rise suddenly. If the subduction zone is under water (as is common), the upthrust will create a ridge of water that becomes a tsunami as a spreads away from the earthquake. Earthquakes on strike-slip faults like the San Andreas cause lateral movement along the fault without upthrust and so typically do not cause tsunamis. The recent earthquake off the coast of Japan was a megathrust earthquake as was the 2004 Indian Ocean earthquake. California can be hit by tsunamis. The Cascadia subduction zone runs underwater from northern California, past Oregon and Washington. The Cascadia zone may be overdue for a megathrust quake: Recent findings concluded the Cascadia subduction zone was more hazardous than previously suggested. The feared next major earthquake has some geologists predicting a 10% to 14% probability that the Cascadia Subduction Zone will produce an event of magnitude 9 or higher in the next 50 years, however the most recent studies suggest that this risk could be as high as 37% for earthquakes of magnitude 8 or higher. Geologists have also determined the Pacific Northwest is not prepared for such a colossal earthquake. The tsunami produced may reach heights of approximately 30 meters (100 ft). http://en.wikipedia.org/wiki/Cascadia_subduction_zone