(KERO) - The City of Ridgecrest is no stranger to earthquakes. A similar event in Los Angeles would have had a much greater impact.SEARLES VALEY, Calif. This community was pretty well prepared and it is sparsely populated. However, we can learn that being prepared for large earthquakes and their aftermaths (such as unstable slopes, landslides, fires from burst gas lines and soil liquefaction) minimizes the impact on the communities affected by the quake. People often get complacent and stop thinking that a big earthquake may strike. Is there anything new we can learn about quakes after the ones that took place this weekend?įirst, this area (southern California)-although known to be seismically active-has been relatively quiet for some time. However, no one expects one on any particular day, so that is always a surprise. The Eastern California shear zone is just one of these-so no, conceptually, the earthquake is not surprising. The stresses associated with this plate boundary (most people think only of the San Andreas fault as marking the boundary) is distributed over several fault systems. In southern California, the Pacific plate is moving northwest relative to the North America plate that is moving southeast. A shear zone (as the name implies) is an area of the Earth’s crust that is fractured in a series of subparallel faults that accommodate shear movement along a plate boundary. This series of earthquakes occurred in what is known as the Eastern California shear zone. People should expect aftershocks to taper off with time, but in the near term, they could feel shaking for weeks to months, or maybe years.Īre these large quakes expected (based on historical patterns and what we know about seismic activity) or was this a surprise to those who research and study earthquakes? The July 4 quake was preceded by smaller shocks and the aftershock interval between the July 4 quake and the July 6 quake included approximately 250 magnitude 2.5+ earthquakes. Aftershocks are smaller in size (by definition) than main shocks or foreshocks (earthquakes that precede the main shock). The aftershock duration typically varies with the size of the main shock. How long should people be worried about another quake in the aftermath of these? Although earthquakes are plotted as a dot on most maps, faults are really big structures.Īfter the two quakes, experts discussed the percentage likelihood of a third one. In the earlier July 4 quake, the earthquake nucleated a bit deeper, but then traveled towards the surface (according to one model I have seen). This, in addition to the size of the quake, led to a lot of shaking and ground failure (i.e., cracks, some landslides) that you have seen in the media. The 7.1 earthquake is estimated to have originated at a depth of about 8 kilometers, which for seismologists, is considered shallow. What exactly does this mean? Is that area extremely unstable now? These earthquakes left a crack so big that it can be seen from space. Lorraine Wolf, geosciences professor in the College of Sciences and Mathematics and director of the Office of Undergraduate Research, discusses the recent earthquakes in California.
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