‘San Andreas’ stands out as a hallmark disaster blockbuster that brings together the scientific community in explaining the real danger we’re in.
Would we have given any thought to a quake shattering the foundations of San Francisco, Los Angeles or San Diego, had it not been for Johnson’s ‘San Andreas’ to craftly combine science and fiction? How about terrifying tsunamis swallowing entire landmarks?
Probably not. Now that the movie sparked the debate and a trail of geology studies is ensuing on the horizon, a recent study from the Legg Geophysical consultancy talks of how real the danger of a tsunami is under the current geological conditions of Southern California.
Let’s look at it this way. There is no cause for panic-inducing thoughts. Awareness and knowledge are the keywords instead. The San Andreas Fault, vilified in the blockbuster is by no means capable of producing a quake of a 9.0 magnitude.
Let alone tsunamis, which are caused by underwater faults and movements, not land faults as San Andreas is. Impressive in length, San Andreas does not reach into the sea.
However, Mark Legg explains in the study, there are a number of connected seafloor faults just offshore Southern California. And these may mean trouble if activated. They are located within just 90 miles of the Californian Coast and count over 20 million years of age. So they have been lurking around for quite a while.
And the truth is they could potentially spark quakes of 8.0 magnitude and bring about tsunamis. However, even these would not be the terrifying type that hit the Japanese coast in 2011.
The generic name for the area where these seafloor faults can be found is the California Continental Borderland. The two largest potential trouble makers here are the Santa Cruz-Catalina Ridge Fault, as well as the Ferrelo Fault.
Along with the smaller sized faults they are interwoven with, they cover an approximate area of 4,500 miles.
In support of Legg’s study, Paul Umhoefer, geologist at the Northern Arizona University, commented:
“The more connected the faults are, the more they can cause larger earthquakes. The more detailed data that was gathered in this study is important for judging whether there is an earthquake and tsunami hazard.”
What Mark Legg’s study emphasizes is that a hazard definitely exists and should realistically be considered. Yet, the geological arrangement of Southern California cannot create quakes or tsunamis that would unleash a super destructive force.
This type of natural disasters are caused in subduction zones. Southern California doesn’t feature subduction zones in its geology.
Rather, what happens in the Southern California seafloor faults is a process Legg describes as transpression. This entails that one fault slipping sideways compresses its two sides, causing them to eventually rupture. At the moment when this happens, the seafloor rises as an effect.
This sends impulses up and then directs them towards shore. Since such quakes are small in magnitude, the tsunamis are also quite small in length and width.
That is not to say caution is not recommended. Simply put, there are no grounded reasons for panic.
Image Source: overpassesforamerica.com
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