• Stress and strain

• Stress: A force exerted per unit area within rocks or other Earth materials

• Strain: Deformation (size, shape, and orientation) of rock materials caused by stress

• Rock strength: Rock’s ability to stand a magnitude level of stress before rupture

Causes for Earthquakes (1)

Stress

Body forces :gravitySurface forces: friction

Stress on a plane: tractionNormal and shear component

From Stein Wisession 2003

Strain

What is an earthquake?

Probably Namazu escaping at his guardian GodsOr Poseidon getting angry???

An earthquake is a release of strain accumulated on a fault

• Earthquake: Sudden release of strain energy caused by rock rupture when the stress is higher than the rock strength or the friction on the fault surface (faulting)

Causes for Earthquakes (2)

Stick Slip

From Marshak, 2005

In the case of rocks alreadyCut by a fault

The story of a Rock,the Wilson Cycle

From Plummer, McGeary and Carlson, 2001

QUELLMECHANISMEN

Im Falle tektonischer Beben kann man 3 grudlegende Quellmechanismen unterscheiden:

Die Länge der Bruchflächen rangiert zwischen ein paar Metern für kleine Beben und mehr als 1000 km für sehr große Beben.

Abschiebung

normal fault

Aufschiebung

reverse fault

Seitenverschiebung

strike-slip fault

Double couple:

This guarantee the conservation of moment

?

Extension:Normal fault

Compression:Thrust or Reverse fault

Conservative baoundary:Strike slip fault (transform fault)

QUELLMECHANISMEN

Beispiel: Quellmechanismen und Tektonik

Subduktion, Aufschiebung,

Nord Amerika über Pazifik Seitenverschiebung

Bookshelf faulting