Paicines – At least 50 earthquakes have rocked the Pinnacles
National Monument in the past week, however most were probably only
aftershocks of a larger quake and are no cause for concern,
according to Stephanie Hanna of the U.S. Geological Survey.
Paicines – At least 50 earthquakes have rocked the Pinnacles National Monument in the past week, however most were probably only aftershocks of a larger quake and are no cause for concern, according to Stephanie Hanna of the U.S. Geological Survey.
Earthquakes in the Pinnacles this week have ranged from 1.6 to 4.4 in magnitude, according to USGS data updated Tuesday. The 4.4 quake was recorded on Tuesday, and Hanna said the smaller quakes that have happened since have mostly been aftershocks. Since Tuesday’s 4.4 quake, there have been 41 of these smaller earthquakes, according to USGS data updated Friday.
Almost all the quakes have been centered about 6 miles northwest of the Pinnacles, and most have been shallow, less than 4 miles beneath the surface, according to reports.
“It’s very common after a 4.4 to have lots of aftershocks; this isn’t really an unusual pattern. A 4.4 would be considered light, but it’s higher than what we usually experience,” Hanna said.
After the San Simeon earthquake in 2003, – a magnitude 6.5 – Hanna said there were “hundreds” of aftershocks.
Pinnacles Park Ranger Peter Szydlowski said Friday the earthquakes have been mostly minor, and haven’t caused any damage at the park.
The 4.4 quake at the Pinnacles, which are located near the San Andreas Fault, likely had no effect on the fault line running through San Juan Bautista, Hanna said, because the quakes were not directly on San Juan’s fault line.
“Fault lines are like tree branches, and a lot of the smaller ones are like the sticks and twigs, so they wouldn’t really be affected,” Hanna explained.
Scientists are interested in studying the Pinnacles quakes to learn more about the southern segment of the potentially dangerous Hayward Fault, the Associated Press reported. The most recent estimates by seismic experts say there’s a 26 percent probability that within the next 30 years a quake with a magnitude of at least 6.7 will strike the segment, which lies roughly between San Leandro and Fremont, according to the AP. It last ruptured in 1968 with a devastating quake estimated at a magnitude of 7, causing death and severe damage throughout the area , even toppling several buildings in San Francisco.
But Hanna said scientists probably won’t be studying this recent wave of earthquakes to learn more about the natural disasters.
“I think this is just another earthquake in earthquake country,” she said.
The Associated Press
contributed to this report.
Jessica Quandt covers politics for the Free Lance. Reach her at 831-637-5566 ext. 330 or at [email protected].
