Assignment 1

Official identification of the event of interest. 1. Provide the latitude, longitude, date, depth, magnitude and description for the earthquake identified here via IRIS’s Wilber 3. [3 marks] Latitude: 37.2251 ° N Longitude: 37.0209 ° E Date: 2023-02-06 01:17:34 UTC Depth: 10.0 km Magnitude: mww 7.8 Description: Independently validate this event’s epicenter. 2. From the “Wilber 3: Select Stations” page here , select seismograms for at least three stations that recorded this earthquake. a. Report the stations used by completing Table 1 below. (Note: “CASY” is a placeholder entry. It should only remain in the table if you intend to make use of it. Marks are awarded here for completing the table and including it in your submission.) [6 marks] b. Click on the “Show Record Section” to view the seismographs corresponding to the stations you selected. 1 Then adjust the time range so that data is reported until 1 minute after the S-wave arrival. 2 i. Capture a screenshot (see example below in Figure 1) that includes the stations you have chosen and their corresponding seismograms. [3 marks] ii. For each of your stations, determine the P-S wave arrival time difference in minutes and seconds (MM:SS). 3 Add this data to Table 1. [3 marks] iii. Using travel times curves for P and S waves (Figure 2 below), determine the corresponding distance in kilometers. Add this data to Table 1. (Hint: Including or referencing a diagram may prove useful.) [3 marks] iv. State in words the meaning of this distance in kilometers. [2 marks] c. State in words the meaning of this distance in degrees. (Hint: Including or referencing a diagram may prove useful.) [2 marks] 3 Note that the arrival time of the S wave (blue vertical bar) is relative to that of the P-wave arrival (red vertical bar at time 0:00:00). 2 This ensures the S-wave arrival appears in your plot of the records. 1 Note that not all of the stations you selected may have observed the event of interest. Therefore, ensure you select at least three stations that actually recorded the event.

Station (ID & Name) Latitude (°) Longitude (°) Distance (°) P-S wave difference (MM:SS) Distance (km) LSZ - Luska, Zambia -15.28° 28.19° 53.16° 7:40 6x10^3 PMSA - Palmer Station, Antarctica -64.77° -64.05° 127.76° 13:50 14x10^3 QIZ - Qiongzhong, Hainan Province, China 19.03° 109.84° 65.19° 8:40 7x10^3 Table 1. Details for selected stations and event specifics. (Note: You are expected to provide a completed version of this table in your submission.) 3. Access IRIS’s “Earthquake Triangulation” resource. a. Before opening the resource itself, review the instructions here - especially the section entitled “IF YOU HAVE SEISMOGRAMS AND WANT TO DETERMINE THE EARTHQUAKE EPICENTER”. b. Using the Earthquake Triangulation app here : i. Estimate the epicenter of the earthquake using the distance data in kilometers from your Table 1. The epicenter should be identified via the app using a marker.

2. State the corresponding location of the epicenter in terms of latitude and longitude. Add this data to Table 2 below. [1 mark] Turkey Latitude: 36.98° Longitude: 37.01° c. Using NOAA’s distance calculator here : i. Determine the accuracy (in kilometers) of the Question 3(b)(i)(2) epicenter location relative to the official determination stated here in Question 1. Add this to Table 2 below. [2 marks] ii. Determine the accuracy (in degrees) of the Question 3(b)(ii)(2) epicenter location relative to the official determination stated here in Question 1. Add this to Table 2 below. [2 marks] iii. Which of these estimates proves to be more accurate in practice? Why do you think this is the case? [2 marks] - I find the estimate in degrees more accurate in practice since the data is from a reliable website with information on earthquakes. What makes my estimate in kilometers is because it's not based on my own estimate from a P-wave and S-wave travel time graph and having to eye what the distance is. Distance Estimation Latitude (°) Longitude (°) Accuracy (km) Kilometers 35.24° 40.05° 352km Degrees 36.98° 37.01° 30km

Table 2. Epicenter determination for the event of interest using length and angular measures for triangulation. (Note: You are expected to provide a completed version of this table in your submission.) 4. The Moment Tensor ‘beachball’ for this event can be found here . a. Using the ‘beachball’ explanation here , identify the focal mechanism for this earthquake. [1 mark] - Using the “beachball” explanation I was able to identify that the earthquake in Turkey is a strike slip focal mechanism. b. Based on the focal mechanism (Question 4(a)) alone, identify the most-likely Plate Tectonic context for this event. [1 mark] - Transform boundary 5. By making use of its magnitude, include the Question 1 earthquake in the Figure 10.17(a) compilation. (Note that there is a copy of this figure from the textbook below.) a. Which ‘great earthquake’ is the Question 1 earthquake only slightly smaller than? [1 mark] - San Francisco 1906 (7.9) b. Which energy event is the Question 1 earthquake comparable to? [1 mark] - Mt. St. Helens 1980 Eruption c. How many times stronger (in terms of magnitude) the Question 1 earthquake relative to the Northridge earthquake of 1994? [1 mark] - The Turkey earthquake is 1.164 times stronger than the Northridge earthquake 6. Based on the aftershocks movie and heatmap , is there a case to be made for a ‘more involved’ Plate Tectonic context? (That is, more involved than the simple answer expected for Question 4(b).) [2 marks] - Based on the aftershocks and using the “beachball” explanation, the most involved Plate Tectonic context would be the transform boundary. Furthermore, the aftershock clip showed multiple strike-slip faults/”beach balls” and a source claimed that the earthquake was caused by the Arabian plate slide horizontally against the Anatolian plate. 43 marks total Resources http://ds.iris.edu/wilber3/find_stations/11654089 https://www.nhc.noaa.gov/gccalc.shtml https://www.iris.edu/app/triangulation/ https://global.shakemovie.princeton.edu/science.jsp?q=Beachball

Figure 2. Travel time curves for P and S waves.

Figure 10.17(a) from the textbook.