What is earthquake focal mechanism?

A focal mechanism, or “beachball”, is a graphic symbol that indicates the type of slip that occurs during an earthquake: strike-slip, normal, thrust (reverse), or some combination. It also shows the orientation of the fault that slipped. Let’s look at the simplest example, a strike-slip fault.

What is a focal mechanism solution?

Focal mechanism solutions are simply fault plane solutions for earthquakes- meaning that they tell us the orientation in 3-D space of two potential fault planes that may have produced the seismic wave signal associated with the earthquake. The dip of a vertical fault is 90o. The dip of a horizontal fault is 0o.

What is a fault plane of an earthquake?

The fault plane is the planar (flat) surface along which there is slip during an earthquake.

What is the mechanism of an earthquake?

The condition for an earthquake to occur is as follows: the tectonic force exceeds the sum of the fracture strength of rock, the friction force of fault boundary and the resistance from obstacles. Therefore, the shallow earthquake is characterized by plastic sliding of rocks that break through the obstacles.

What are the fault types?

What is a fault and what are the different types?

  • Normal Fault Animation.
  • Thrust Fault Animation.
  • Blind Thrust Fault Animation.
  • Strike-slip Fault Animation.

How do you plot focal mechanism?

Plot single focal mechanism by clicking button on map toolbar, and then double clicking on the earthquake location on the map. This will plot on the map, and you can drag it to the location where you want it.

What is origin of earthquake?

The earthquakes originate in tectonic plate boundary. The focus is point inside the earth where the earthquake started, sometimes called the hypocenter, and the point on the surface of the earth directly above the focus is called the epicenter.

What are the 3 major types of faults?

Different types of faults include: normal (extensional) faults; reverse or thrust (compressional) faults; and strike-slip (shearing) faults.

Which is the focal mechanism of an earthquake?

Seismologists refer to the direction of slip in an earthquake and the orientation of the fault on which it occurs as the focal mechanism. They use information from seismograms to calculate the focal mechanism and typically display it on maps as a beach ball symbol.

Which is the fault plane responsible for the earthquake?

The fault plane responsible for the earthquake will be parallel to one of the nodal planes, the other being called the auxiliary plane. It is not possible to determine solely from a focal mechanism which of the nodal planes is in fact the fault plane. For this other geological or geophysical evidence is needed to remove the ambiguity.

Which is the focal mechanism of a strike slip fault?

The map at left shows a left-lateral strike-slip fault oriented roughly N-S, and the focal mechanism at right represents the fault orientation and the sense of slip on the fault. The shaded quadrants indicate compression and the light quadrants indicate extension. (Public domain.) Two Possible Focal Mechanism Solutions.

How is a fault plane solution useful in seismogenic volumes?

Fault plane solutions are useful for defining the style of faulting in seismogenic volumes at depth for which no surface expression of the fault plane exists, or where the fault trace is covered by an ocean.