#earthquake-dynamics

#earthquake-dynamics

The United States Geological Survey reported that the earthquake struck early Tuesday evening local time at a depth of about 237 km, which is significant as shallower earthquakes are felt more strongly at the surface.

A magnitude 3.4 earthquake rumbled in the South Bay on Tuesday morning, according to the U.S. Geological Survey. The temblor struck at 6:48 a.m. and its epicenter was approximately 15 miles south of San Jose and 5 miles east-northeast of Gilroy. At least two small aftershocks were reported in the area shortly after the initial shaker; those shocks measured magnitude 1.3 and magnitude 1.0 respectively.

The rods are the central element of a novel seismic-responsive structural system that is designed to help the building snap back to its original shape in the event of a major earthquake. Their trick is an embedded cluster of taut cables made from a highly flexible compound called a shape-memory alloy that's capable of bending under tension-like the lateral shaking in a California earthquake-and then straightening out.

Although Kansas has no active volcanoes, the region marks the southern reach of the Midcontinent Rift System, a massive tectonic event that nearly split North America apart in Earth's distant past. When magma forced its way through the crust during that period, it left behind hardened igneous rock and deep fractures that remain buried thousands of feet underground.

An earthquake measuring at a preliminary magnitude of 4.3 shook Sonoma County on Saturday morning around 9:22 a.m., according to the U.S. Geological Survey. The temblor struck about 3.7 miles north-northwest of the Geysers, close to Healdsburg in the North Bay. Originally the quake was measured at a preliminary magnitude of 3.9 but that was revised to a preliminary 4.3 later in the morning by the USGS.

The city passed legislation nearly 18 months ago requiring property owners to retrofit their multi-story, wooden-frame buildings with at least three units constructed before 1990. It delayed implementation, however, when the federal government rolled back significant funding to facilitate the repairs. But after a court-granted injunction required the release of some of those federal funds, the city approved a $1.6 million pilot financing program in hopes of rolling out a larger critical life-safety initiative in the future.

Earthquakes usually strike without warning. But sometimes they come in clusters dozens or even hundreds of small quakes concentrated in one area over days or weeks. Geologists call these clusters earthquake swarms, and while they can be unsettling, scientists say they rarely signal that a major quake is imminent. Unlike the familiar pattern of a single large earthquake followed by aftershocks, swarms consist of many small quakes without a clear mainshock.

A magnitude 6.2 earthquake hit western Japan on Tuesday, the country's meteorological agency said. The quake was relatively shallow, the meteorological service said, and struck around 10:18 a.m. local time (0118 GMT). There was no tsunami threat, the agency added. The US Geological Survey measured the quake at magnitude 5.7. The quake occurred in Shimane prefecture in northwestern Japan, impacting the cities of Matsue and Yasugi and nearby areas in Tottori prefecture.

The flurry of quakes rattled close to a relatively unknown fault called Blue Cut, according to Kate Scharer, a research geologist for the U.S. Geological Survey's Earthquake Hazards Program in Pasadena. "This happened in Joshua Tree National Park, a beautiful part of the world where many people have actually probably been and unknowingly traversed near this fault," Scharer told SFGATE. "This is a good reminder that there are many other faults besides the San Andreas in California that can give us a little jolt."