California Earthquakes August 26, 2012

California Earthquakes August 26, 2012

A series of moderate earthquakes struck California on Sunday, August 26, 2012, the U.S. Geological Survey (USGS) said .

The strongest registered at magnitude 5.4 and was recorded at 1:57 p.m. local time (20:57 UTC).  Its epicenter was located at 5 km (3 miles) North of Brawley, California.

The USGS recorded more than two dozens of earthquakes that jolted California on Sunday, mostly originating from Brawley. Their Richter Scale readings ranged from magnitude 3.0 to 5.4.

Below were the preliminary magnitude counts of some of the quakes:

Magnitude 4.0 12:16 p.m - 6 km (4 miles) N of Brawley, California
Magnitude 4.6 12:20 p.m. - 5 km (3 miles) N of Brawley, California
Magnitude 5.3 12:31 p.m. - 5 km (3 miles)  N of Brawley, California
Magnitude 4.9 12:33 p.m. - 3 km (2 miles) NW of Brawley, California
Magnitude 4.3 12:40 p.m. - 6 km (4 miles) WNW of Brawley, California

There were no immediate reports of serious damage or injuries from the earthquakes.

4.0-magnitude Earthquake Jolts Southern California

California Earthquake Map, June 13, 2012

An earthquake with a Richter Scale reading of magnitude 4.0 struck Southern California on Wednesday evening, June 13, the United States Geological Survey (USGS) said.

According to a USGS bulletin, the quake, which has a depth of 9.8 km (6.1 miles), hit at 8:17 p.m. local time. Its epicenter was 3 km (2 miles) north of Yorba Linda, California, about 28 miles southeast of Los Angeles.

There are no immediate reports of damage or casualties.

The temblor was followed by a 2.4 magnitude aftershock a few minutes later.

California earthquake more mellow than East Coast quake

California earthquake vs Virginia quake

Wondering why the 6.0-magnitude California earthquake in 2004 was felt only 200 miles away (as far away as San Francisco and Los Angeles) while the less powerful magnitude 5.8 Virginia quake last Tuesday felt as much as 500 miles away (as far north as Ottawa, Canada; as far south as Georgia, and as far west as Chicago)?

According to U.S. Geological Survey (USGS) seismologist Lucy Jones, it is because of the differing geologic conditions of these two areas.

"The crust out in the East Coast is older, colder and harder, and does a better job transmitting the energy. So it's felt over a much wider area," Jones told LA Times.

In contrast, Jones added that in California, "the bad news is we have a lot of faults. The good news is all those faults break up our rock. And just like a cracked bell doesn't resonate as well as a solid bell, our cracked-up crust [weakens] the waves as they pass through. It dies off pretty rapidly.
"But out there, the rocks are old and cold and hard, and do a lovely job of transmitting the energy," Jones said.

A USGS article had also explained the phenomenon.

"Western rock is relatively young, which means it absorbs a lot of the shaking caused by earthquakes. Thus, western earthquakes result in intense shaking close to the epicenter, but fade more quickly the farther the earthquakes travel.

"In the eastern United States, on the other hand, the rock is far older, and so earthquakes can have a much larger and more widespread impact. Earthquake energy can therefore spread farther and have a greater impact." USGS wrote.