There has been a great deal of talk about earthquake preparedness since the Mexico quakes devastated the regions affected and we are happy to see that Southern Californians are finally beginning to wake up to the realization that a major earthquake is on the horizon.
There are other hazards associated with an earthquake that also need to be addressed but one subject in particular that Southern Californians have not even begun to talk about. We are referring to earthquake generated tsunamis. Yes, tsunamis! This is a very real threat that should not be ignored.
When it comes to a Southern California tsunami, a real life offshore earthquake and tsunami would not exactly follow Hollywood’s script for a washout of Los Angeles as depicted in the 2015 release of San Andreas starring The Rock (Dwayne Johnson) and California will not fall into the ocean as so many hope for. The tsunami hazard does deserve more attention than it has received which is little to nothing. Some earthquake and geology experts insist the hazard has been looked at but acknowledge further study is needed.
There are two underwater fault zones that concern experts which are the Santa Cruz – Catalina Ridge fault and the Ferrelo fault. Those two faults were determined to be subject to horizontal strike-slip forces as well as vertical compression. Computer models show that those offshore faults are capable of producing magnitude 8 earthquakes. Experts have found evidence of vertical movement up to 10 feet in a region known as the Continental Borderland which can cause tsunami waves. This region has been called a “smoking gun”.
Southern California earthquake expert Lucy Jones said there has been evidence that tsunami waves have hit Southern California’s coast going back to 1812, when a huge wave apparently generated by a 7.2 magnitude quake in the Santa Barbara channel pushed a 283 ton trading ship a half mile inland and then pulled it back out to sea intact. The ship survived the ordeal.
Anytime someone mentions tsunami, people think think of the 2004 Sumatra incident or even the 2011 Japan incident that affected the Fukushima nuclear power plant. Those particular tsunamis were generated in subduction zones, where tectonic plates dive beneath another. The faults in the Continental Borderland probably would not produce dramatic tsunamis but they do pose a risk but not as big a risk as those seen in big subduction zones.
The zone that is closest to Southern California is the Cascadia Subduction Zone which lies off the coast of Northern California, Oregon and Washington state. A cascadia quake in the year 1700 produced a tsunami so big that is caused major damage on Japan’s pacific coast. No matter where a a Southern California tsunami is generated, even a 1 to 2 meter surge could impact our ports.
When it comes to Southern California tsunamis, the key is not to worry but to prepare for one especially if you live or work along the coast. As part of tsunami preparedness, know where the evacuation routes are and know how to get to higher ground if a warning is activated.