In a few places along compressional bends, two thrust-faulted mountain ranges may converge, forming a rapidly subsiding basin between the faults. This forms a distinctive geometry known as a flower or palm tree structure, with a vertical strike-slip fault in the center and branches of mixed thrust/ strike-slip faults branching off the main fault. Many of the faults that form along compressional bends have low-angle dips toward the main strike-slip fault but progressively steeper dips toward the center of the main fault. Examples of compressional (or restraining) bends include the Transverse Ranges along the San Andreas fault and Mount McKinley along the Denali fault in Alaska. Sion of the extra volume of crust compressed into the bend in the fault. Movement along fault segments with exten. The differences between theoretical and actual fault orientations leads to the formation of segments that have pure strike-slip motions and segments with compressional and extensional components of motion.Įxtensional segments of transform boundaries form at left steps in left-slipping (left lateral) faults and at right steps in right-slipping (right lateral) faults. The faults are typically subparallel because they form along theoretical slip lines (along small circles about the pole of rotation), but the structural grain of the rocks interferes with this prediction. They never occur as a single fault, but rather as a set of subparallel faults. Transform faults in continents show strike-slip offsets during earthquakes and are high angle faults with dips greater than 70°. In this video, the boundaries between three different tectonic plates and the earthquakes that result from their interactions are explored.Transform boundaries on the continents include the San Andreas fault in California, the North Anatolian fault in Turkey, the Alpine fault in New Zealand, and, by some definitions, the Altyn Tagh and Red River faults in Asia. Lassen, and landslides on coastal cliffs, the natural hazard the state is linked with is earthquakes. Three people died in this mall in Santa Cruz during the 1989 Loma Prieta earthquake.Īlthough California is prone to many natural hazards, including volcanic eruptions at Mt. Other significant earthquakes in California include the 1989 Loma Prieta earthquake near Santa Cruz ( Figure below) and the 1994 Northridge earthquake near Los Angeles. ![]() The San Andreas Fault runs through the San Francisco Bay Area. In the San Francisco Bay Area, the Hayward Fault was the site of a magnitude 7.0 earthquake in 1868. While most of those earthquakes cannot even be felt by people nearby, occasionally one is very strong. ![]() In total the San Andreas Fault system produces around 10,000 earthquakes a year ( Figure below). There are many other faults spreading off the San Andreas, to take up the plate motion. ![]() About 3,000 people died and 28,000 buildings were lost, mostly in the fire that followed the earthquake. ![]() The quake's epicenter was just north of San Francisco. The largest earthquake in recorded history on the San Andreas Fault occurred in 1906. It is the plate boundary between Pacific and North American plates. The San Andreas Fault that runs through much of California is an enormous transform plate boundary. This is because the plates slide past each other without moving up or down. These quakes at transform faults originate at shallow foci. Transform plate boundaries produce enormous and deadly earthquakes.
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