GEOL 240Lg 1st Edition Lecture 9 Outline of Last Lecture I Review Stresses II Plate tectonic III Elastic Rebound Theory IV Energy in rocks V States with major earthquakes Outline Current Lecture I Basin and Province II Western Boundary the East Side of the Sierra Nevada III Constellation of GPS Satellites IV San Andreas Fault and Wasatch V Basin Range VI Major Earthquakes and their magnitudes Current Lecture Basin and Range Province activities we are worried about Reno the western boundary the east side of the sierra Nevada sierra just means mountain range how high is Mt Whitney Owens lake elevation 4k Sierra Nevada is the footwall Hilton creek normal fault e sierra Nevada picture Salt Lake City and Wasatch front a mirror image of the Sierra Nevada There s lots of brick construction there til 1980 people did not appreciate that they live around this big faults GPS site velocities showing east west extension rate across basin and range Wastch fault extending along mountain front Big range big normal faults beautiful moraines Places where you actually see the plane San Andreas Fault and Wastch fault along the oldest planes that were studied No big earthquake in history time of Wastch Why are all the speeding records done at Salt Faults Utah Because it is the flattest place Lake mutt water saturated cities built on this lake will not do well during huge earthquakes yet to come San Andreas Fault right lateral The biggest the longest fault in California it stores out energy faster than any fault in California so it releases faster and generates the largest earthquakes much bigger than any south of Cascadia The dominate fault The total rate in which it move 5cm per year 35 50 plate rate 70 of movement is brought by San Andrea It is not the plate boundary 5 is in the basin range the rest is east of the sierra Nevada a thousand kilometers long slipping 35 mm per year 27 of constellation at GPS satellites in geosynchronous orbit these satellites are microwave receivers encoded in them you can tell exactly where you are in the earth with this these are incredibly useful for earthquake signs 1906 Mw 7 9 San Francisco earthquake need to know it was about magnitude 8 six fingers of slip It rupture a 450km length of SAF slipped 5m of average slip 15km down dip width What happens when you go down on the earth temperature and pressure 15 km this is how much earthquakes go deep Why don t they go deeper You increase temp and pressure and eventually you reach a point when instead of bending and breaking they just flow and then they get weaker The other big one the san Andreas Fault has produced is 1857 Fort Tejan Mw 7 9 Ruptured 350km of SAF 5m of average slip 15 km down dip width creeping section of SAF 150 km long central part of SAF rocks slide continuously rather than storing up elastic strain energy 1906 stopped at the North end 1857 stopped at south end SAF Hayward Fault Calaveras Fault 3 major strands of SAF system in the san Francisco bay area Figure 1 the San Fran bound train at point Reyes station that was tipped on its side during the 1906 San Fran earthquake Why did San Fran say that earthquake didn t do any damage Because they had a fire insurance and insurance were going to rebuild city