Seismology

Expect a far more powerful earthquake than last week's magnitude 7.6 temblor to hit the devastated Indonesian city of Padang and surrounding areas in the next few decades. That's the word from a team of leading seismologists, who said the worst is yet to come, although they cautioned that predicting the timing of earthquakes is an inexact science at best. After a three-day review of seismic evidence using global-positioning equipment, scientists with the Earth Observatory of Singapore, or EOS, found that the Padang earthquake did little to relieve the stored tension at the juncture of two tectonic plates.

Leon Knopoff, a UCLA researcher who was widely regarded as the father of theoretical seismology, died of respiratory failure Jan. 20 at his home in Sherman Oaks. He was 85. Knopoff did pioneering research in "how an earthquake works," said his colleague, UCLA geophysicist Paul M. Davis. "He demonstrated that an earthquake can be represented in terms of forces ? then reduced it to a much simpler mathematical model of forces acting within the Earth. " He was among the first to apply computer modeling to earthquakes, using applied mathematics to develop sophisticated representations of what was happening beneath the Earth's surface.

The earthquake that occurred 400 miles underneath Bolivia on Wednesday night, and was felt thousands of miles north in Canada, was upgraded by scientists Thursday to at least a magnitude 8.2 and called a unique opportunity for study of Earth's structure.

Ever since we heard an Iranian cleric explain that scantily clad and promiscuous women are the cause of earthquakes, we just can't get Carole King out of our heads: "I feel the earth move under my feet, I feel the sky tumbling down." Of course, that's not the kind of sexual seismology Hojatoleslam Kazem Sedighi had in mind when he told worshipers in Tehran last week that women who dress immodestly corrupt young men and lead them to adultery, thereby increasing earthquakes. "What can we do to avoid being buried under the rubble?"

Hundreds of years before European settlers founded Seattle, an earthquake fault under what is now the Kingdome shook the area with a mighty force, lifting parts of the Puget Sound shore by 20 feet, triggering massive landslides and pushing a tidal wave toward Canada.

"Hiroo Kanamori knows more about earthquakes than anyone . . . although he probably says, 'I don't understand' more than any other geophysicist," read the citation when the Seismological Society of America gave its annual medal to the Caltech scientist two years ago. This probably captured as well as anything the essence of Kanamori, 57, director of the Caltech Seismological Laboratory.

Why does one earthquake feel so much different from another? The earthquake that rattled through Southern California on Wednesday may have felt quite different to people who experienced the Montebello quake last June 12, even if they were in the same place both times. Workers in office buildings in downtown Los Angeles, for example, reported feeling a sharp jolt from the 4.5 magnitude Montebello quake, whereas Wednesday's 5.5 temblor produced a long rolling motion.

At the Parkfield Cafe in this tiny ranch town tucked inside the Coast Range, scientists and reporters huddle like a pack of expectant fathers. Townsfolk eye them warily. Never have so many strangers gathered in such a small spot to wait for--even root for--the earth to shake. They started to overrun this hamlet on the San Andreas Fault at midnight Monday, shortly after a 4.

Scientists trying to analyze the ongoing Southern California earthquake sequence focused their interest Monday on a section of the San Andreas Fault after several aftershocks were detected near the state's longest and most infamous quake zone. Cautioning that they cannot be certain what it all means, Caltech and U.S.

To mark today's 30th anniversary of the devastating San Fernando-Sylmar earthquake, the state Department of Conservation released a new map Thursday identifying in great detail the geologic materials in the San Fernando Valley and how they respond to seismic activity. With the map, geologists and engineers have the most complete picture to date of the Valley's unique geological makeup, giving them another tool to evaluate an area's susceptibility to shaking during an earthquake, experts say.

The catastrophic quake that struck Haiti on Tuesday involved a collision of lethal circumstances: a massive, shallow eruption below a densely populated city with few, if any, building codes. The magnitude 7.0 quake occurred near the boundary between two major tectonic plates, the Caribbean and North American plates. Most of the movement along these plates is what is known as left-lateral strike-slip motion, according to the U.S. Geological Survey, with the Caribbean plate moving eastward in relation to the North America plate.

Expect a far more powerful earthquake than last week's magnitude 7.6 temblor to hit the devastated Indonesian city of Padang and surrounding areas in the next few decades. That's the word from a team of leading seismologists, who said the worst is yet to come, although they cautioned that predicting the timing of earthquakes is an inexact science at best. After a three-day review of seismic evidence using global-positioning equipment, scientists with the Earth Observatory of Singapore, or EOS, found that the Padang earthquake did little to relieve the stored tension at the juncture of two tectonic plates.

The 2004 Sumatra earthquake that set off a deadly tsunami also seems to have caused more earthquakes along the San Andreas fault in the last few years, according to a study from UC Berkeley. The study analyzed 20 years of data in the Parkfield area, which sits on the fault, and found that the disastrous earthquake weakened the fault, changing both the frequency and strength of earthquakes in the area. "So you will have many earthquakes, but the magnitude will be smaller than expected," said Taka'aki Taira, a seismologist at UC Berkeley who headed the study.

It's one of the great mysteries of Southern California seismology: Every couple of years, the remote desert area around the Salton Sea is shaken by swarms of small to moderate earthquakes that often last several days. The swarms returned this week, with the area recording more than 200 temblors since Saturday -- including several that were felt Wednesday.

Large earthquakes have rumbled along a southern section of the San Andreas fault more frequently than previously believed, suggesting that Southern California could be overdue for a strong temblor on the notorious fault line, a new study has found. The Carrizo Plain section of the San Andreas has not seen a massive quake since the much-researched Fort Tejon temblor of 1857, which at an estimated magnitude of 7.

Southern California stands a much greater chance of a huge temblor in the next 30 years than Northern California, according to a statewide earthquake forecast released Monday. The report, which brought together experts from the U.S. Geological Survey, USC's Southern California Earthquake Center and the State Geological Survey, also found that California is virtually certain to experience at least one major temblor by 2028. According to the research, the chance of a 6.

"Only fools, charlatans and liars predict earthquakes." That unkind assessment of those who claim to know when the Earth is most likely to shudder has been attributed to the legendary pioneer in seismology, Charles Richter. The quote has become part of the folklore of the dark art of predicting earthquakes, and many would say it is as true today as when it was allegedly muttered by the Caltech scientist who gave the world its earthquake magnitude scale.

In a search for possibly destructive hidden thrust faults beneath Southern California, earthquake scientists plan to set off 60 small explosions in October along a 100-mile line extending from Seal Beach through the San Gabriel Valley to the Mojave Desert. The blasts, which each will use 250 to 4,000 pounds of ammonium nitrate, are to be detonated underground mostly on public property belonging to the military, the federal Bureau of Land Management, the U.S.

las vegas -- Engineers moved some structures at the Yucca Mountain nuclear waste dump after rock samples indicated a fault line unexpectedly ran beneath their original location, an Energy Department official said Monday. Allen Benson, a spokesman for the U.S. Department of Energy in Las Vegas, said project adjustments were made in June. "In the spring we discovered the true course of the Bow Ridge fault line. As a result we moved locations several hundred feet" to the east, he said.

Earthquakes that struck Southern California over the last century killed more than 200 people and caused billions of dollars in damage. But new research to be released today says the Los Angeles area may actually be in the midst of a prolonged seismic lull. Geologists examined the size and frequency of quakes going back 12,000 years, finding patterns of heavy and lighter seismic activity every 1,000 to 1,500 years.