Over a thousand tiny earthquakes detected along this US state in 8 months: Study

California experienced a record number of tiny earthquakes recently, a study of Long Beach and Seal Beach areas noted saying that a thousand tiny tremors have been recorded over eight months in the state.

Majority of the quakes were shallow and reached depths less than two kilometres below the surface, but the region is at risk of bigger tremors, the study said.

The study was published in Seismological Research Letters for which the researchers used three dense nodal arrays consisting of thousands of sensors to detect and locate seismic events. Small events can be detected at “sufficient signal‐to‐noise levels during the night when urban noise is relatively low”, the researchers said.

“Our results suggest the zone of high hazard at the surface may therefore be much wider than the Alquist-Priolo zone indicates,” the authors of the study wrote.

The “seismicity pattern also compares well with some newly identified faults from reflection seismic surveys”, the study noted.

Researchers Yan Yang and Robert Clayton wrote in the study that the Long Beach earthquake of 1933 may have ruptured the Newport-Inglewood fault. Big earthquakes would most likely begin six to ten kilometres below the surface “shallow seismicity suggests that there are many possible paths for a rupture to propagate to the surface”, Yan Yang said, “The Newport-Inglewood fault along its entire length, as well as the whole Los Angeles Basin, could benefit from such studies.

“This would help to see if there are faults that have not been detected with the permanent seismic network or through geologic mapping,” Yan Yang added.