GEOL 106 - LEC 11

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Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
Prof.
Semester
Fall

Description
Hazard City For now peruse the map reading exercise. We will get email with problems and then do them via hazard city, and email them back to the marker that was assigned to the student. Again you will get all this information via email shortly. Earthquake Hazards (continuing from lecture 9) 1.Surface Faulting: structures on the fault will be disrupted by the tearing motion. So do not build directly on active faults. ex. San Andreas Fault 2.Ground Shaking: this is generally the greatest threat to buildings and people. In a big earthquake, the shaking can be sever even 100’s of kilometers away from the epicenter. The amount of shaking also depends on the nature of the soul and rocks in the area. 3.Ground Failure: a) Landslides b) Liquefaction of soils 4.TSUNAMI: Japenese word for Harbour Wave. Colloquial: tidal wave. Seismic sea wave. Generated by earthquake at sea. Veolcity can go several 100 km in length and up to traveling speed of 500 to 800 km an hour. (commercial jet place) • Causes o Seafloor earthquakes o Underwater landslide o Collapse of the flank of a volcano into the sea o Submarine volcanic explosion o Impact of meteorite into the ocean 5.FIRES – ex. The 1906 fire in sanfransico 6.Disruption of water supplies & disease 7. is human induced >>>> 8. Human induced seismic hazards • Damn construction Loading of earth by water changed the stress on the fault Water infiltration below dam can lubricate faults (possible dam failure) rock burst due to pressure on the mine shaft walls. Mini explosions. • Mining Underground blasting can de-stabilize the rocks. Can lead to earthquakes. Risk Analysis 1.Understand the hazards 2.Determine the risk from that hazard for the of interest (risk = Ph x Sh) Assess seismic risk of area • a ) Locate and determine nature of faults in the area. o 1.Look on the ground and rom the air but there can be HIDDEN faults. o 2.Set up your seismometers to help locate faults, only effective for faults that have moved since you set up the seismometers (note : fault zones are very complex) o 3. o 4. • B) Study history of quakes in the area o Which faults are active? o How often do “big” quakes occur? (in our region of interest) o 1. Set up seismometers  gives idea of which faults are most active  gives some idea of frequency and magnitude of quakes  critical to collect as long a seismic record as possible (eg. Let look at Canada – where are the high earthquake prone zones)  Is the artic region high risk? – no (because the population is low) – so lets look more closely at western Canada and eastern Canada o 2. Determine RECURRENCE INTERVAL for “big” earthquakes in the area (ie. How often do “big” quakes happen?_)  “Big” ---- means “greater that magnitude 7)  happen rarely How do we determine RECURRENCE INTERVAL for big >magnitude 7 quakes?
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