Search results
Feb 15, 2021 · A fault is a fracture or crack along which two blocks of rock slide past one another. This movement may occur rapidly, in the form of an earthquake, or slowly, in the form of creep (Figure 6.18). Types of faults include strike-slip faults, normal faults, reverse faults, thrust faults, and oblique-slip faults.
When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other. The fault surface can be vertical, horizontal, or at some angle to the surface of the earth.
Aug 28, 2024 · Fault, in geology, a planar or gently curved fracture in the rocks of Earth’s crust, where compressional or tensional forces cause relative displacement of the rocks on the opposite sides of the fracture. They range in length from a few centimeters to many hundreds of kilometers.
- The Editors of Encyclopaedia Britannica
- SLU Eas-A193 Class Notes Faults and Faulting Contents
- Introduction
- Earthquakes and Faults
- Fault Structure
- Fault Classifications
- Stress and Strain
- Elastic Rebound
Rocks are very slowly, but continuously moving and changing shape. Under high temperature and pressure conditions common deep within Earth, rocks can bend and flow. In the cooler parts of Earth, rocks are colder and brittle and respond to large stresses by fracturing. Earthquakes are the agents of brittle rock failure. A fault is a crack across whi...
When an earthquake occurs only a part of a fault is involved in the rupture. That area is usually outlined by the distribution of aftershocks in the sequence. We call the "point" (or region) where an earthquake rupture initiates the hypocenter or focus. The point on Earth's surface directly above the hypocenter is called the epicenter. When we plot...
Although the number of observations of deep fault structure is small, the available exposed faults provide some information on the deep structure of a fault. A fault "zone" consists of several smaller regions defined by the style and amount of deformation within them. The center of the fault is the most deformed and is where most of the offset or s...
Active, Inactive, and Reactivated Faults
Active faultsare structure along which we expect displacement to occur. By definition, since a shallow earthquake is a process that produces displacement across a fault, all shallow earthquakes occur on active faults. Inactive faultsare 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 f...
Faulting Geometry
Faulting is a complex process and the variety of faults that exists is large. We will consider a simplified but general fault classification based on the geometry of faulting, which we describe by specifying three angular measurements: dip, strike, and slip.
Faults and Forces
The style of faulting is an indicator of rock deformation and reflects the type of forces pushing or pulling on the region. Near Earth's surface, the orientation of these forces are usually oriented such that one is vertical and the other two are horizontal. The precise direction of the horizontal forces varies from place to place as does the size of each force. The style of faulting that is a reflection of the relative size of the different forces - in particular is the relative size of the...
Stressis a force per unit area or a force that acts on a surface. When I described the types of forces associated with the different styles of faulting (in the section "Faults and Faulting"), I was describing stresses (the force per unit area on the fault). Frictionis a stress which resists motion and acts in all natural systems. For earthquake stu...
As you know, some regions repeatedly experience earthquakes and this suggests that perhaps earthquakes are part of a cycle. The effects of repeated earthquakes were first noted late in the nineteenth century by American geologist G. K. Gilbert. Gilbert observed a fresh fault scarp following the 1872 Owens Valley, California earthquake and correlate...
An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.
Identify secondary earthquake hazards. Describe notable historical earthquakes. Crustal deformation occurs when applied forces exceed the internal strength of rocks, physically changing their shapes. These forces are called stress, and the physical changes they create are called strain.
People also ask
How do we know if a fault is causing an earthquake?
What is a fault in geology?
How do scientists classify a fault?
What is the difference between a normal fault and an earthquake?
Mar 6, 2019 · To understand the risk that different areas of the U.S. face for earthquake hazards, we need to know where faults are and how they behave. We know a fault exists only if it has produced an earthquake or it has left a recognizable mark on the earth’s surface.
