![]() ![]() The above-mentioned Garlock fault is a left-lateral strike-slip fault. The USGS explains the difference between a left-lateral strike-slip fault and a right-lateral strike-slip fault, stating that when viewed from either side, the left-lateral strike-slip fault’s far rock block moves to the left. Encyclopedia Britannica further defines a transform fault as a type of fault in which two tectonic plates slide past one another. Transform faultĪ transform fault, as shown below, is situated along a plate boundary where the movement and motion are mostly horizontal. According to the USGS, the recent magnitude 6.4 earthquake on Decemnear Ferndale in Humboldt County was the result of strike-slip faulting. Another example of a strike-slip fault is the Garlock fault, which triggered the magnitude 7.1 Ridgecrest earthquake in 2019. Strike-slip faults also are found in the Rocky Mountains. The San Andreas fault is an example of strike-slip motion, in which faulting occurs when blocks of rock slide past one another horizontally. If you live in California, you probably have heard of the notorious San Andreas fault, which cuts through a wide swath of the Golden State. A reverse fault is sometimes called a thrust fault if the dip angle of the fault is shallow.īoth the destructive magnitude 6.7 San Fernando/Sylmar earthquake in 1971 and the deadly magnitude 6.7 Northridge quake in 1994 occurred on thrust faults, according to the Southern California Earthquake Center. The USGS notes that these types of faults are common in Japan. But it differs from a normal fault in that it moves upward in relation to the block of rocks below. Reverse Thrust FaultĪ reverse thrust fault is also known as a dip-slip fault. Normal faults are common in the western United States, in mountain ranges and along ocean ridges. In normal faults, the faulting occurs when blocks of rocks slip past one another. Normal faults are dip-slip faults that move downward in relation to the blocks of rock below. The USGS notes that its definitions of these faults are adapted from the book, The Earth, by Frank Press and Raymond Siever.Ī normal fault is the most common type of fault. The USGS describes some of the different types of faults below. Scientists use the angle of the fault in relation to the surface (known as the dip angle) and the direction of fault slips to classify the different types of faults in geology. The Earth’s faults can be broken down into a few main categories or types of faulting depending on their movement. While California’s 15,700 faults might sound like a lot, there are thousands upon thousands of different types of earthquake faults and different types of fault lines as part of the North American Plate and other plate boundaries around the world. A fault line often is plotted on earth sciences maps to represent a fault.Īn earthquake hazards map, such as this one on the USGS website, provides seismic hazards mapping information to help you become more familiar with the earthquake hazards in the specific area in which you live. A fault line, sometimes also known as a fault trace, is where a fault can be mapped or observed on the surface. There can be confusion over the difference between what is a fault and what is a fault line. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other.” This movement may occur rapidly in the form of an earthquake-or may occur slowly, in the form of creep. The United States Geological Survey (USGS) explains that “faults allow the blocks (of rock) to move relative to each other. The sudden, rapid movement of these blocks of rock is what leads to earthquakes.Ī fault is a “weak point within a tectonic plate where pressure from the Earth’s surface can break through and cause shaking in an earthquake.” Faults vary in length and seldom follow a straight line. From the Golden State’s urban cities to scenic coastal areas, most of us live within 30 miles of a fault, which can best be described as a crack or fracture between two blocks of rock in the Earth’s crust. Despite its natural beauty, abundant sunshine, majestic mountains, plentiful agriculture, and proximity to the Pacific Ocean, California, from a geologic standpoint, is far from perfect. ![]()
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