3. Earthquake timing Below is a table of recorded arrival times from a recent Mw5.8 earth- quake in Pawnee, Oklahoma. This is real data provided by the USGS. Times are given as hours:minutes:seconds. Use matlab to help you do the following exercise (2 pts each section): a) Plot the arrival time differences (t.-t) from the table at the end of this problem set against the arrival times of the P-waves (tr). b) Use the command "polyfit" to fit the data. The command "poly- fit(x,y,l)" will fit the data in vectors x and y with a first-order poly- nomial (which is a straight line). The first number returned in the command window is the slope and the second one is the y-intercept. (See "doc polyfit" for more information). Plot the line with the data and report the slope and intercept. c) Derive a relationship between the slope and the ratio of P-wave ve- locity to S-wave velocity (Cp/cg). d) Report the ratio of P-Wave to S-wave velocity for the measurements in the table e) Use the information to now figure out the time of occurrence (origin time of the earthquake. f) Assume an S-wave velocity of 3 km/s in the crust. How distant is the earthquake from the closest seismometer in the table? Please hand in a print out for your script for the matlab parts of this problem and a printout of your plot. Station Name P Arrival Time Sarrival time RH11 12:02:50.3 12:02:54.5 QUOK 12:02:50.8 12:02:55.6 BLOK 12:02:52.4 12:02:58.3 OK031 12:02:53.8 12:03:00.9 OK030 12:02:54.5 12:03:01.6 RH07 12:02:54.7 12:03:02.4 T35B 12:02:55.8 12:03:03.9 KNG1 12:02:57.7 12:03:08.3 KAN12 12:03:07.4 12:03:25.0 3. Earthquake timing Below is a table of recorded arrival times from a recent Mw5.8 earth- quake in Pawnee, Oklahoma. This is real data provided by the USGS. Times are given as hours:minutes:seconds. Use matlab to help you do the following exercise (2 pts each section): a) Plot the arrival time differences (t.-t) from the table at the end of this problem set against the arrival times of the P-waves (tr). b) Use the command "polyfit" to fit the data. The command "poly- fit(x,y,l)" will fit the data in vectors x and y with a first-order poly- nomial (which is a straight line). The first number returned in the command window is the slope and the second one is the y-intercept. (See "doc polyfit" for more information). Plot the line with the data and report the slope and intercept. c) Derive a relationship between the slope and the ratio of P-wave ve- locity to S-wave velocity (Cp/cg). d) Report the ratio of P-Wave to S-wave velocity for the measurements in the table e) Use the information to now figure out the time of occurrence (origin time of the earthquake. f) Assume an S-wave velocity of 3 km/s in the crust. How distant is the earthquake from the closest seismometer in the table? Please hand in a print out for your script for the matlab parts of this problem and a printout of your plot. Station Name P Arrival Time Sarrival time RH11 12:02:50.3 12:02:54.5 QUOK 12:02:50.8 12:02:55.6 BLOK 12:02:52.4 12:02:58.3 OK031 12:02:53.8 12:03:00.9 OK030 12:02:54.5 12:03:01.6 RH07 12:02:54.7 12:03:02.4 T35B 12:02:55.8 12:03:03.9 KNG1 12:02:57.7 12:03:08.3 KAN12 12:03:07.4 12:03:25.0
