Find the point for 24 seconds on the left side of the chart below and mark that point. Measure the distance between the first P wave and the first S wave. Permission granted for reproduction for non-commercial uses. To get an earthquake location, we need information from three recording stations so we can find the intersection of three circles. The Láska's empirical rule provides an approximation of epicentral distance in the range of 2 000 − 10 000 km. One minute intervals are marked by the small lines printed just above the squiggles made by the seismic waves (the time may be marked differently on some seismographs). Use the compass to draw a circle around the station the correct distance from the epicenter. Then, the distance d to the epicenter is: d = V p * t p = 6.01 km/sec * 429.3 sec = 2,580.2 km . Compute the distance of the epicenter from each of the stations using the formula: d= Td x 100 km 8 seconds Where: d = distance (km) Td = time difference in the arrival time of P-wave and S-wave (seconds) 7. Set the Radius to the distance of station B . Use the Travel Time Chart to determine the distance from the epicenter. 5. For Phoenix the distance to the epicenter is 600 kilometers, and from Las Vegas the distance to the epicenter is 380 kilometers. 1. Finally, with three stations, you can pinpoint the location. The distance from the epicenter is determined by the length of time it takes for the Primary and Secondary waves to arrive at the recording station. Repeat this process for at least two more stations. • All other content is ©2007 Michigan Technological University. 51 4 3 2 1 0 500 2500 3000 1000 1500 2000 Distance in miles We've done the first one for NYC. Do all four stations (the fourth station is for accuracy). Therefore, we draw a circle with a radius equal to the distance from earthquake. The point where all of the circles overlap is the approximate epicenter of the earthquake. Since the question is "how far," you should use the distance formula, Distance = Velocity X Time. To get the epicenter, it is necessary to triangulate the results worked out in the previous step. RYAO Answer: The distance of the epicenter from the seismic station is equals to 127 km (minimum). The, Place a ruler (or straight edge) on the chart between the points you marked for the distance to the epicenter and the amplitude. Touch buttons to watch movie of seismic waves, or touch "Walk-run" button to see wave travel can be demonstrated with a class. It should look something like a piece of a ruler. You may need to download version 2.0 now from the Chrome Web Store. Cloudflare Ray ID: 625780b55c274d8a This number will be used to tell you how far your seismograph is from the epicenter of the earthquake. Each station on the interactive map recorded an earthquake with a characteristic seismogram. If the epicenter of the earthquake is 215 kilometers away, that equals 2.15 centimeters on the map. S - P Lag. The epicenter will be located in the region where the circles overlap. Here is the link to the activity itself: goo.gl/3kB29Students learn how to determine the epicenter of an earthquake using seismographic data. Otherwise, all that you'd know is that the ground shook. Triangulation is required to determine exactly where it happened. 6. from the epicenter. It may help to do the first one together. Analysis of the waves can yield the distance between the sensor and the epicenter. Measure the amplitude of the strongest wave. If a lag time of 15 seconds corresponds to 100 miles of distance to the epicenter, how far is the epicenter from another recording station, if that lag time is 30 seconds? Set the Radius to the distance of station C . In this case, the first P and S waves are 24 seconds apart. Finding the Distance to the Epicenter and the Earthquake's Magnitude Figure 2 - Use the amplitude to derive the magnitude of the earthquake, and the distance from the earthquake to the station. In this case, the first P and S waves are 24 seconds apart. Use a seismograph, attached to bedrock, to record P and S Waves. distance = (30 s / 8 s) × 100 km (cancel out unit second) = 3. 2. To determine the difference between the arrival of the P waves and S waves, scroll … All maps are different. Another method of locating an earthquake is to use the P-wave arrival-time minus origin-time (P - … With distance data from a second station, you can narrow this down to either of two points of intersection of the circles. Your IP: 138.201.247.196 How can we calculate the distance to an epicenter? Do the same thing for the distance to the epicenter that the other seismograms recorded (with the location of those seismographs at the center of their circles). Measure difference in P- and S-wave arrival times, then use data from the Earthquakes 1 - Recording Station Gizmo to find the distance of the epicenter from each station. This is done by drawing a circle around the location of the seismic station that has an equal radius between the station and the distance the waves traveled. Dr. Robert Butler briefly describes how to use seismic travel-time curves. Seismic wave - Wikipedia. Another way to prevent getting this page in the future is to use Privacy Pass. The intersection of the 3 cirles gives epicenter location. One seismic station can only tell you the distance to an earthquake. The circle represents all possible locations at this fixed, determined distance from the seismograph. Finding the Distance to the Epicenter and the Earthquake's Magnitude. 3. Figures 1 and 2 are from Bolt, 1978. 75 × 100 km = 375 km This data means that if the time difference in the arrival of p-wave and s-wave is 30 seconds, the distance of the seismic station to the earthquake epicenter is 375 km. Larger image The Southern California Seismic Network (SCSN) records data from more than 370 seismic stations. Which two places could the epicenter be located now? epicenter-to-station distance corresponding to the S minus P time will be displayed to the left of the seismogram. Performance & security by Cloudflare, Please complete the security check to access. The seismogram tells you how far, but not from what direction the p and s waves came from. Once distances from the epicenter have been calculated from at least three seismographic measuring stations, the point can be located, using trilateration. All of the circles should overlap. A second seismograph, which can be hundreds or thousands of miles away, can generate a similar plot. This describes a circle with the seismograph at the center. You can't determine the distance to the epicenter given only one time. epicenter, but you still don't know exactly where the earthquake occurred. The seismographs show that the time difference for the arrival of the P and S wave at each station is proportional to the distance of the station from epicenter. _____ _____ 5. You can observe the P- and S-wave arrivals on a seismogram to calculate how far away an earthquake was from your station. Roll over the stations to see the epicenter triangulated. Using an earthquake recording station, learn how to determine the distance between the station and an earthquake based on the time difference between the arrival of the primary and secondary seismic waves. Determine the arrival times of the P-wave and the S-wave. This is where the compass, the map, and the other seismograph records come in. On your map, one centimeter could be equal to 100 kilometers or something like that. Use the scale in the middle of the maps to find the distance from the station. All the data are transmitted automatically to Caltech/USGS in Pasadena for processing and distribution of information such as epicenters, magnitudes, and ShakeMaps. Upper station : Distance = 1065 km Lower Station Distance = 1350 km The larger the lag time, the larger the distance of the station from the epicenter. The spot where those three circles intersect is the epicenter (Figure 13.12). Great-circle arcs are drawn on the globe using the distance of the earthquake to the station as a radius. The later the P wave arrival time, the larger the distance of the station from the epicenter. To determine the distance of an earthquake epicenter: 1. All the arcs should intersect at a common point - the epicenter. 2. The distance is 355 kilometers. The distance between the beginning of the first P wave and the first S wave tells you how many seconds the waves are apart. The circles from these two stations cross each other at two points. Each seismograph station is at a different distance from the epicenter and records the seismic waves as they arrive at the station. Please enable Cookies and reload the page. Have the students record their answers for each station in the Distance from the Epicenter column of Table 1. This should be done with all three and it should produce an overlap. On a map, the distance of an epicenter from a seismic station can be represented as a The epicenter is at the surface directly above the hypocenter (also called the focus) of the earthquake somewhere below the surface. 4. Use this data to find the epicenter in the Earthquakes 2 - Location of Epicenter … Look on the two circles on the map. Further instructions for using AmaSeis in S minus P earthquake location are available in the “Using AmaSeis” tutorial referenced in section 1, above (see section 3.6 in the tutorial). Using your compass, draw a circle with a radius equal to the number you came up with in Step #2 (the. Using the arrival times of the P and S waves from 3 different stations distances to epicenter can be determined. The epicenter is at the surface directly above the hypocenter (also called the focus) of the earthquake somewhere below the surface. In practice, there are some difficulties with this method. Using the distance scale on the station map, set your compass to the correct distance and draw a circle on the map, centered on the station. Check the scale on your map. To figure out just where that earthquake happened, you need to look at your seismogram and you need to know what at least two other seismographs recorded for the same earthquake. If you know the distance to the epicenter from only one station, then the epicenter could be anywhere on a circle centered on that station. Seismic wave - Wikipedia. • 2. Choose one of the recording stations and measure the computed distance on the map scale ( the scale of the map is 1 cm: 70 km). A circle is drawn from each of the three different seismograph locations, where the radius of each circle is equal to the distance from that station to the epicenter. Compute the distance of the epicenter from each of the stations using this formula: d = time difference x 100 km 8 seconds where: d = distance (km) td = time difference in the arrival time of P-wave and S-wave (seconds) This formula is suited because 8 seconds is the interval between the times of arrival of the P-wave and S-wave at a distance of 100 km. Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. Enter these data in Table 1. You will also need a map of the world, a ruler, a pencil, and a compass for drawing circles on the map. How Do I Locate That Earthquake's Epicenter? You have just figured out how far your seismograph is from the epicenter and how strong the earthquake was, but you still don't know exactly where the earthquake occurred. For example, say your map has a scale where one centimeter is equal to 100 kilometers. from the epicenter. THREE3 stations … Could have been a … • Draw a vertical line from the edge of the paper to the ads in the travel time diagram to determine the distance from the station to the epicenter. Finding the Distance to the Epicenter from a Seismic Station According to the chart, this earthquake's epicenter was 215 kilometers away. Follow me on this. If you know the distance from a station, you know that the epicenter is located on a circle of that radius from the seismic station. Three seismographs are needed. Each station records seismic waves from both near and distant earthquakes. You need the difference in P- and S-wave travel times to determine the distance. 4. Figure out how long the distance to the epicenter (in centimeters) is on your map. The point where your ruler crosses the middle line on the chart marks the. This intersection is the epicenter. Using Distance Values from Three Seismograms to Determine the Location of an Epicenter . (from Bolt, 1978) Measure the distance between the first P wave and the first S wave. 3. If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware. Locate the epicenter of an earthquake by analyzing seismic data from three recording stations. If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. The distance from the epicenter is determined by the length of time it takes for the Primary and Secondary waves to arrive at the recording station. In the sample below that would be … Locate : Turn on the Show station C checkbox. How to use the Earth Science Reference Tables to determine the epicenter of an earthquake from a seismogram.

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