Earthquake and Tsunami Mechanism

Quake rocks Indonesia:

• Magnitude 8.6 in Richter scale.
• Curious by the absence of Tsunamis, explained by nature of Faults.

                            

What are Faults:

• Faults are simply put fractures or weak zones along the earths crust.
• The movements of earthen plates along these fractures are caused by endogenetic forces operating under the earth. When sudden release of energy happens ,this exceeds the strength of rocks to withstand  and release of of energy happens as movement of rocks.
• There are two kinds of movements along the fault plane, vertical(Dip slip movements) and horizontal(Strike slip movements).
• Dip slip movements are further causing either Normal faults or Reverse faults.
• In normal faults tensional forces operate and two rocks along fault lane move in opposite directions,moving upward and downward, here the fault angle is usually more than 45 degrees.
• In reverse faults compressional forces operate and one rock may override another and the fault angle here is usually less than 40 degrees. Reverse faults are usually causing Tsunamis/(2004 for instance).
• The recent Indonesian quake was neither normal or reverse movement rather horizontal, strike slip movement.(two types left or right lateral)
• When both dip and strike movements occur it is said to be Oblique movement, reason for the small waves initially in the Indonesian coast.