What is “surface rupture” in an earthquake?
Surface rupture occurs when movement on a fault deep within the earth breaks through to the surface. NOT ALL earthquakes result in surface rupture. Fault rupture almost always follows preexisting faults which are zones of weakness. Rupture may occur suddenly during an earthquake or slowly in the form of fault creep. Sudden displacements are more damaging to structures because they are accompanied by shaking. • Q: What is meant by “fault creep?” A: Fault creep is the slow movement of faults in the earth’s crust. [EXAMPLES of creep are well known along the Hayward Fault where it crosses highly developed areas in Contra Costa and Alameda Counties.] Page Index General Info: • Q: What is an earthquake? A: An earthquake is caused by a sudden slip on a fault. Stresses in the earth’s outer layer push the sides of the fault together. Stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the rock to cause the shaking that we feel during an earthquake. • Q: W
