Friday, June 24th, 2016

Will the San Andreas Fault in California big Earthquake come soon?

Narada Desk | June 24, 2016 1:55 pm Print
Earthquake prediction is still elusive. The Big One is almost a sure thing, sooner or later, but there is no way to tell when. We don’t even know if earthquakes that do happen release stress or are signs of increasing stress. San Andreas never can deliver 9.6 only 8.3 earthquake, as well tsunami so high like in a movie totally unrealistic. Even scientists who consulted producer sad they over dramatized consequences of San Andreas possible Big One

5.2 is a fairly decent quake , but geologically, they are fairly insignificant.

A San Andreas rupture would be on the order of an 8; lets say 8.2, so three magnitudes higher than the 5.2. How much more energy does an 8.1 release? relative energy released in an earthquake is 10^1.5dM where dM is the difference in magnitude. in this case 3. So the difference is 10^4.5, which is about 32,000. this means that a magnitude 8.2 earthquake releases 32,000 times more energy than a 5.2, or it would take 32,000 magnitude 5.2’s to release the energy of a magnitude 8.2.

Based on the USGS earthquake map, this one in particular happened about 50km (30 miles) from the San Andreas fault, so not only was it small, it wasn’t all that close to the San Andreas fault, so while it is possible that the San Andreas fault or the fault region this earthquake happened along might rupture tomorrow, it is unlikely to be specifically because of this earthquake.

As always, do be prepared for a major earthquake because they can happen at any time. Make sure you have enough water and food for a week along with a battery powered radio, a torch, and some blankets. Also make sure that any shelves, cabinets, heavy ornaments, etc. are secured to reduce the risk of them falling. Be aware that there WILL be aftershocks, and a small risk of an earthquake just as big or bigger on the following days and weeks.

  • Given the size and geometry of the fault(s), the odds of an earthquake above magnitude 8.3 on the San Andreas fault (or any other nearby fault) are somewhere between astronomically low and completely impossible. For a summary of earthquake risks in California,  refer you to the USGS (2008 Bay Area Earthquake Probabilities, etc). A M 8.3 is big, but it isn’t apocalyptic, especially in an area with modern building codes and 49 other states to help absorb the economic impacts.
  • If there is any tsunami associated with an earthquake in the greater Bay area, it will be fairly small and localized. Max size is a few meters at most, and that only if the quake triggers offshore landslides. The San Andreas system (unlike the faults offshore Oregon and Washington) is strike-slip, with two plates sliding past each other (as opposed to one being shoved over the other). As a result, most of the direct offset on the fault is horizontal, not vertical, and tsunamis are generally caused by vertical motion of the seafloor.
  • As to building failures, the movie takes some major liberties, presumably for dramatic effect. The biggest buildings and skyscrapers in this area are actually some of the safest places to be in an earthquake. Modern buildings are built with earthquakes in mind. They have Base isolation and flexible structures that flex instead of breaking. The buildings that colapse will be brick and masonry, for the most part. In this part of the country, such buildings are far less common than on the east coast, precisely because of the earthquake hazard. They still exist, but most people will not be in them. (see also Earthquake resistant structures, and Earthquake engineering)
  • The Hoover Dam is not at risk from the San Andreas fault. There are other faults much closer to that dam that could be a problem, but the San Andreas is too far away across multiple geologic terrains for an earthquake there to seriously damage the Hoover dam. (Recent seismic hazard map from USGS:…)