Anactive fault is afault that is likely to become the source of anotherearthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years.[1]
Active faulting is considered to be ageologic hazard – one related toearthquakes as a cause. Effects of movement on an active fault includestrong ground motion, surface faulting,tectonic deformation,landslides androckfalls,liquefaction,tsunamis, andseiches.[2]
Quaternary faults are those active faults that have been recognized at the surface and which have evidence of movement during theQuaternary Period.[3]
Relatedgeological disciplines foractive-fault studies includegeomorphology,seismology,reflection seismology,plate tectonics,geodetics andremote sensing,risk analysis, and others.[2]
Active faults tend to occur in the vicinity oftectonic plate boundaries, and active fault research has focused on these regions. Active faults tend to occur less within the area of any given plate. The fact that intraplate regions may also present seismic hazards has only recently been recognized.[2]
Various geologic methods are used to define the boundaries of an active fault such asremote sensing and magnetic measurements, as well as other ways. Several types of data, such as seismologic reports or records over time, are used to gauge fault activity. Activity and fault area are correlated, and risk analysis is employed with other factors to determine the potential earthquake hazard.[2]
The geologic conditions andtectonic setting in much of the Western U.S. has resulted in the region being underlain by relatively thin crust and having high heat flow, both of which can favor relatively high deformation rates and active faulting.
In contrast, in the Central and Eastern U.S. (CEUS) the crust is thicker, colder, older, and more stable. Furthermore, the CEUS is thousands of miles from active plate boundaries, so the rates of deformation are low in this region. Nevertheless, the CEUS has had some rather large earthquakes in historical times, including a series of major earthquakes nearNew Madrid, Missouri in 1811–1812, a large earthquake nearCharleston, South Carolina in 1886, and theCape Ann earthquake northeast of Boston in 1755.[3][4]
This article incorporatespublic domain material from websites or documents of theUnited States Geological Survey. This article incorporatespublic domain material from websites or documents of theUnited States Geological Survey. This article incorporatespublic domain material from websites or documents of theUnited States Geological Survey.Authority control databases: National |
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