* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Homework Set 1
Survey
Document related concepts
Casualties of the 2010 Haiti earthquake wikipedia , lookup
2011 Christchurch earthquake wikipedia , lookup
Kashiwazaki-Kariwa Nuclear Power Plant wikipedia , lookup
2010 Canterbury earthquake wikipedia , lookup
2009–18 Oklahoma earthquake swarms wikipedia , lookup
2008 Sichuan earthquake wikipedia , lookup
1880 Luzon earthquakes wikipedia , lookup
April 2015 Nepal earthquake wikipedia , lookup
2010 Pichilemu earthquake wikipedia , lookup
1570 Ferrara earthquake wikipedia , lookup
2009 L'Aquila earthquake wikipedia , lookup
1906 San Francisco earthquake wikipedia , lookup
Earthquake engineering wikipedia , lookup
1992 Cape Mendocino earthquakes wikipedia , lookup
Transcript
Geol 344: Earthquakes and Seismic Hazards Spring 2006 Homework Set 3: Fault Friction, Seismogenic Faults, and Seismic Waves 1. Measurements of principal stresses at two different depths in the Earth's crust at a hypothetical location indicate the following stress magnitudes (in megaPascals, MPa): Depth: 5 km 10 km 1 115 MPa 240 MPa 3 14 MPa 54 MPa (i) Use this data to construct Mohr circles on a vs n graph (shear stress versus normal stress) for the two depths shown. Important: you MUST use graph paper because the vertical () and horizontal (n) scales must be exactly the same in order for this to work properly. Label each axis in increments of MPa. (6) (ii) Assuming that these Mohr circles define the strength of the rock at the given depths, construct a Mohr envelope that is tangent to both circles. What is the general equation of this line? (3) (iii) Use the Mohr envelope to deduce the inherent shear strength of the rock (So) (i.e., the y-intercept) and the coefficient of friction of the rock () (i.e., the slope of the line or in other words, the tangent of the angle of slope of the line). (4) (iv) At a depth of 10 km, what is the normal and shear stress acting on a fault that is oriented at an angle of 30 to 3? (read your answer directly off the graph using the angle 2) (4) (v) Would the fault in question (iv) be able to produce an earthquake? How can you tell? (2) (vi) At a depth of 10 km, what would the angle need to be for a fault to be optimally oriented for failure? Explain your reasoning. (4) (vii) How much pore pressure would need to be added to the system at a depth of 5 km in order for the Mohr circle to touch the failure line and potentially create an earthquake? (3) (viii) Which fault orientation would be prone to producing earthquakes for the situation in question (vii) (i.e., what value?). (2) (ix) If 1 represents the vertical principal stress at this location, what type of faults would we expect to be active in this region, and why? (3) 2. On 27 June, 1988, a magnitude 5.4 earthquake was recorded at three Californian seismograph stations (BKS, JAS, and MIN), as shown on the attached map. The difference Geol 344: Earthquakes and Seismic Hazards Spring 2006 between P and S wave arrival times are shown in the table below, along with the calculated epicentral distances based on the S-P time interval. California Seismograph Station Data Station S-P (sec) Distance (km) BKS 21.0 190 JAS 20.4 188 MIN 12.9 105 (a) Use this data to determine the location of the earthquake epicenter on the attached map.(8) (b) Use your determined epicenter location to determine why this earthquake occurred where it did and when it did. Be sure to refer to the Coulomb failure criterion in your answer (i.e., provide a reason for the earthquake based on the physics of fault failure). (6) 3. Could a seismograph attached to a buoy just below the ocean surface detect the seismic waves from an earthquake that occurred below the ocean floor? Also, would the distance to the earthquake be calculable? Explain your reasoning in each case. (5) [50] Geol 344: Earthquakes and Seismic Hazards Spring 2006