Lecture 8-10 - Stresses and Faults

Question 1

Describe the most famous offset in the San Andreas Fault

Answer 1

• Basement offset (~600 km)
• Pinnacles-Neenach offset (315 km post 23.5 Ma)
• Palaeobathemetry offset (325 km, post late Oligocene

Question 2

Describe the graphs of horizontal displacement, shear strain and the dislocation model for coseismic strain release and interseismic strain accumulation

Answer 2

Question 3

What did Noriega et al (2006) use to interpret steady interseismic motion along the San Andreas Fault and what is the crustal motion model they interpreted derived from?

Answer 3

• Buried screw dislocation was used to interpret motion
• Crustal motion model derived from geodetic measurements of benchmark motion - GPS + older trilateration

Question 4

What is the heirarchical approach to delineation of tectonically active zones?

Answer 4

In order of size:

• System: km scale data integration
• Structure: 10s of m scale structural characterisation
• Event: cm scale measure of timing and process

Question 5

What two models are there of fault growth?

Answer 5

1. Radial propagation
2. Segment linkage

Question 6

How do faults develop?

Answer 6

• Radial propagation: Faults lengthen through time and accumulate displacement. Linear length/displacement relationship.
• Segment linkage: when two segments link length increases suddenly but not displacement. Non-linear length/displacement relationship

Question 7

What two features can we use to trace fault development through time?

Answer 7

• Rivers: how do they respond to changes in the system
• Sediment deposition: if the route to a source is cut out the sediment from that source will disappear in the basin

Question 8

In what two ways can deformation patterns be studied?

Answer 8

• Geodesy (short term)
• Palaeoseismology (long term)