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Active amd Inactive Faults

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Prinian Curtis

on 22 January 2015

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Transcript of Active amd Inactive Faults

Faults may be classified according to their level of activity
Active faults
- are known to
have recently generated
an earthquakes within
10 000 years.
Inactive faults
- do not show
signs of ever having
generated an earthquake
in last 10 000 years, but may
possibly still generate an
earthquake in the future.
Active Faults
Active faulting is considered to be a geologic hazard - one related to earthquakes as a cause. Effects of movement on an active fault include strong ground motion, surface faulting, tectonic deformation, landslides and rockfalls, liquefaction, tsunamis, and seiches.

Quaternary faults are those active faults that have been recognized at the surface and which have evidence of movement in the past 1.6 million years - the duration of the Quaternary Period.

Related geological disciplines for active-fault studies include geomorphology, seismology, reflection seismology, plate tectonics, geodetics and remote sensing, risk analysis, and others.

Location: Active faults tend to occur in the vicinity of tectonic 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
Inactive Faults
Since a shallow earthquake is a process that produces displacement across a fault, all shallow earthquakes occur on active faults. Inactive faults are structures that we can identify, but which do no have earthquakes.

are structures that we can identify, but which do no have earthquakes. As you can imagine, because of the complexity of earthquake activity, judging a fault to be inactive can be tricky, but often we can measure the last time substantial offset occurred across a fault. If a fault has been inactive for millions of years, it's certainly safe to call it inactive. However, some faults only have large earthquakes once in thousands of years, and we need to evaluate carefully their hazard potential.
Reactivated faults
Form when movement along formerly
inactive faults can help to alleviate
strain within the crust or upper
mantle. Deformation in the New
Madrid seismic zone in the central
United States is a good example of
fault reactivation. Structure formed
about 500 Ma ago are responding to
a new forces and relieving strain in
the mid-continent.
Fault may appear to be Inactive
Small type of fault movement.

Fault creeps happens without any associated earthquake activity, but it may be noticeable because of ground subsidence and deformed structures that overlie the creeping fault
Active, Inactive and Reactivated Faults
Prepared by: Maria Abigaile Mendoza
Rai Angela Ibanez
Fault may appear to be Inactive but i
t may actually generate earthquakes hundreds of years apart, and may not have moved within the recorded history of the area around the fault.

But if the area around the fault changes easily, such as due to rapid erosion or widespread urban development, the interpretation of fault activity becomes more difficult if it only moves suddenly every few hundred years.
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