GEOL 106 Lecture Notes - Lecture 8: Elastic Energy, 1906 San Francisco Earthquake, Fault Scarp
3 Jan 2017
School
Course
Professor
à Mastering Geology Password
Readings: Chapter 3&4
Earthquake
Risk Analysis and Risk Management
•
Seismic risk analysis and risk management
Generic Approach to Risk Analysis and Risk Management
Risk Analysis
•
Understand the hazard
•
Determine the risk from that hazard for the region of interest (Risk = PH x
SH)
The first step in a risk analysis of a natural hazard: understand the hazard
What causes earthquakes?
•
1906 San Francisco Earthquake – provided case study to see how
earthquakes occur
•
Fault: a break or crack in rocks along which there has been appreciable
displacement
o
Strike-slip Faults: Horizontal movement (^)
o
Dip-Slip Faults: Sub-vertical or vertical movement resulting in a
fault scarp
§
Normal Dip-Slip Fault: Vertical movement, sliding down the
ramp (ßà)
§
Revers Dip-Slip Fault: Vertical movement, pushed up the ramp
(àß)
•
Large earthquakes can be associated with any of the three faults, but the
biggest are associated with Revers Dip-Slip
•
Many rivers occur along faults, because the broken up rocks can be more
easily washed away and we often build dams on them if they make
canyons
•Elastic Rebound Theory: the ridged part of the earth can store elastic
energy, when it breaks the elastic is released
•Earthquakes are associated with faults, earthquakes happen when either
oA fault forms
oThere is an episode of movement on a pre-existing fault
•In both cases, stored energy is released
•For a big earthquake fault motion needs to be only a metre or so
Where do earthquakes occur?
•Focus: the point source for energy release on the fault
•Epicentre: the point at the earth’s surface that is directly above the focus
oCloses place at earth’s surface to the focus
•Seismometers allow us to
oDetect the energy from a quake
oMeasures distance to an earthquake and thus locate it
oMeasures the energy released during an earthquake
•Inertial Mass: dense block, “a mass at rest tends to stay at rest”
•When the ground shakes the mass will draw straight lines or squiggles if
there is an earthquake
What energy do they release? (Lectures 9-12)
What exactly cause damage? (Lectures 9-12)
Lecture'8
Sunday,(December( 25,(2016
2:43(PM
