Two more earthquakes shook southern Mexico Saturday, further rattling a country still coming to grips with the devastation from stronger temblors earlier this month.
Meanwhile, Californians are anxious about a possible Big One, because of the recent major quakes – all seemingly hitting in the “ring of fire,” where about 90 percent of seismic activity occurs.
A 6.1-magnitude Mexico earthquake Saturday morning was centered in Oaxaca state near Matias Romero, a town about 275 miles southeast of Mexico City, the U.S. Geological Survey said. Roughly speaking, the epicenter was between the centers of this month’s two more violent earthquakes – the 7.1 magnitude temblor that hit Tuesday closer to the capital, and the 8.1 magnitude quake that struck Sept. 8 off the southern Pacific coast, near Chiapas state.
Another 4.5-magnitude quake hit Oaxaca at 7:06 p.m. Eastern. That temblor occurred at a depth of 8.9 kilometers, according to initial readings by USGS.
In Oaxaca, some highways and a bridge that had been damaged during the Sept. 8 earthquake collapsed, Mexico’s federal police said.
Mexico City did not appear to have sustained significant damage in the earlier and stronger of Saturday’s two quakes, said the country’s office of the secretary of public security.
Warning sirens sounded in Mexico City after the morning quake was detected, interrupting rescue operations at some of the dozens of buildings that collapsed from Tuesday’s earthquake.
At least 90 percent of the world’s earthquakes hit in the so-called “ring of fire” stretching from New Zealand to Chile through Asia and toward the Americas.
And the chances of California experiencing a major earthquake has peaked, say researchers from the U.S. Geological Survey.
Tom Jordan, director of the Southern California Earthquake Center, said: “We know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable. We are fortunate that seismic activity in California has been relatively low over the past century.”
Researchers scoured through the latest data from the state’s active geological faults to determine the likelihood of an earthquake there.
Their findings showed the probability that California will experience a magnitude 8 or larger earthquake in the next 30 years has increased from about 4.7 percent to about 7 percent.
Fears are growing in the wake of a 6.1-magnitude earthquake hitting New Zealand Wednesday as it caused tremors off the coast of Japan and Indonesia. California is located in the same path.
It comes as Mexico continues to battle to rescue survivors from toppled buildings after its devastating 7.1-magnitude quake Tuesday killed 230 people.
Seismologists are concerned that there has been an unusually high amount of activity along the fault in the past week. One scientist branded the activity “unusual.”
“Earthquakes in California and Mexico differ in ways that are important to understand – if we are to learn lessons that allow us to better prepare for them in the future,” said seismologist Jean-Paul Ampuero, a professor in the Seismological Laboratory at CalTech. “First, the tectonic activity in each area is different: California sits at the boundary between two plates that rub each other horizontally. The plates off the shore of Mexico and the rest of the Pacific ‘ring of fire,’ an area of intense seismic activity, rub against each other vertically. As a result, Mexico has bigger earthquakes. The biggest Mexican earthquakes happen offshore and create tsunamis, but the earthquakes themselves are far from Mexico City.”
The biggest Californian earthquakes happen inland on the San Andreas Fault, he said, and as a result generate no tsunami.
“Though they are smaller than earthquakes like the one we are seeing cause such devastation in Mexico, they occur dangerously close to Los Angeles.”