By John Davis
The pressure wave came first in the form of an audible boom followed by the shock wave .The earthquake was caused by a fault one mile North West of Marina del Rey, directly off of Venice Beach. If you stood at the end of the Venice Pier it would be very near.
Other active offshore faults exist in and near the bay. A geologic (study of the earth) fault is a crack in the rock layers below caused by various underground pressures that cause rock layers to settle and shift.
If you can imagine a tasty but brittle graham cracker breaking you will understand what a fault is. Now imagine a stack of delicious crackers that are intact with the broken one at the bottom.
The weight of the crackers on top can cause the cracked one below to shift. Sometimes distant earthquakes can move the local fault just enough to trigger another quake.
When this happens an earthquake occurs at depth and the effects are felt at the surface. The underground origin point is called the epicenter of the quake.
In the case of the Venice Beach Quake the epicenter of the temblor was 4.6 miles below the surface, about the same distance to LAX from Venice. If you have ever walked a mile you can get an idea of how far below the surface that is.
The movement of the rocks can displace the sea and translate into a fast high wave. Sometimes underwater canyons get shaken causing underwater landslides which can also trigger deadly tsunamis. Our local underwater canyon is the Santa Monica Canyon and it abruptly plunges to a depth of 2000 ft with very steep walls.
On January 23 at 7:44 pm residents as far as Santa Monica, Culver City, and Westchester felt the earth move. People closer to the source reported hearing a sort of boom then the jolt. I was in Westchester in my car and felt a gentle ripple. The good news is there was no Tsunami. The other good news is our Councilperson, Bill Rosendahl, had the foresight to insist Tsunami Warning Signs be placed in Venice recently to help people prepare in advance.
The bad news is we still live in earthquake country and should always be prepared with enough water for three weeks, a lot of canned food, a can opener, medicine, a radio with extra batteries or a wind-up unit, and a family plan. You should think in advance about what to do if you are separated from family because of school or work. Discuss what your family will do if this happens so that everyone will remain as calm as possible.
Surviving a disaster starts with a plan. Panic is not an option.