EARTHQUAKE'S EPICENTER SCIENCE 8 POWERPOINT
- 3. Directions: Use triangulation method to locate the earthquake’s epicenter by making three circles from the point of the seismic station. The place where the three circles intersect or nearly intersect is the earthquake’s epicenter and label it. Use and gather the materials below for your activity. Carefully follow the procedure. Answer guide questions and write your answers on the line provided. You may use another sheet of paper for your computations and conversion.
- 4. PROCEDURE: Study the data showing the difference in the arrival time of P wave and S- wave on the three seismic recording stations and complete the table below. Recording Stations Time difference in the arrival time of P- wave and S- wave (Seconds) Distance of Epicenter from the station (km) Computed distance on the map (cm) (1.5 cm: 200km) Ex. Calbayog City 36 Answer: 450km 3.4 cm Batangas 44.8 Puerto Princesa 32 Davao 38.4
- 5. Compute the distance of the epicenter from each of the stations using this formula: Note: 8 seconds is the interval between the time of arrival of the P- wave and S-wave at a distance of 100km. where: d= distance (km) Td= time difference in the arrival time of P-wave and S-Wave (Seconds)
- 6. ANALYSIS QUESTIONS: 1. Where is the epicenter of this hypothetical earthquake? 2. What difficulty will you encounter if you only have data from two recording stations? 3. What do you think is the importance of determining the epicenter of an earthquake?
- 7. How do seismologists determine how strong an earthquake is? What about the damage it can cause?
- 8. Magnitude – is the measurement of the energy released by an earthquake. Ritcher Scale – an instrument used to measure the magnitude of an earthquake. Intensity – is the strength of seismic shaking at a given area or location. Mercalli Scale – used to determine the intensity or the effect of an earthquake on the Earth’s surface.
- 11. SEISMIC WAVES
- 12. SEISMIC WAVES – are energy that travel either through the Earth’s interior or along or near the Earth’s surface. Body Waves – travel through the Earth’s interior. a.Primary Waves(P-waves) – travel the fastest. b. Secondary Waves(S-waves) – transverse in nature. Surface Waves – travel across the Earth’s surface. a. Rayleigh waves - Longitudinal waves (L-waves) – waves having the same direction of vibration as their direction of travel or wave propagation. - Transverse waves – occur perpendicular to the direction of travel or wave propagation. b. Love waves (L-waves) – includes transverse motion.
- 14. SEISMOGRAPH A seismograph is an instrument that can record seismic waves. - Geologists use seismograph(seismogram) to determine how strong an earthquake was. A less powerful earthquake is shown by short wiggly lines, while a powerful earthquake is shown by long wiggly lines.
- 15. Why seismologists need to monitor earthquake activities and locate earthquake epicenters?
- 16. The following are the reasons why seismologist monitors earthquake activities and its epicenter: 1. Public Safety 2. Identifying Risk Zones 3. Understanding Earth’s Structure 4. Forecasting and Research 5. Tsunami Warnings
- 17. Philippine Institute of Volcanology and Seismology (PHIVOLCS) is a service institute of the Department of Science and Technology (DOST) that is principally mandated to mitigate disasters that may arise from volcanic eruptions, earthquakes, tsunami and other related geotectonic phenomena.
- 18. This service institute monitors seismic activities in the Philippines based from their mandates; Predicts the occurrence of volcanic eruptions and earthquakes and their related geotectonic phenomena; Determines how eruptions and earthquakes shall occur and also areas likely to be affected Generate sufficient data for forecasting volcanic eruptions and earthquakes Mitigate hazards of volcanic activities through appropriate detection, forecast and warning system, and formulate appropriate disaster preparedness plans.
- 19. Another purpose of continuously monitoring and gathering data about seismic activities is to figure out larger, bigger and more destructive earthquakes which may strike by mapping out smaller quakes. Therefore, they can give suggestions, precautionary measures, programs for disaster risk reduction and mitigation to be implemented throughout the country. Disaster Preparedness is very vital for all Filipinos’ life saving preparation.
Editor's Notes
- #3: Cities A,B and E Cities C,E and F City D The friction across the surface of the fault holds the rocks together in order that they don’t slip immedieately when pushed sideways. Eventually enough stress builds up and thus sudden slip of the rocks , releasing energy in waves that travel through the rock to cause the shaking that we feel during earthquake.
- #5: Cities A,B and E City D Bec. City D is far from any fault..There is no hazard of ground of ground fissure which could damage the foundation of the house…
- #6: Did you know that several million earthquakes happen every year?. Most earthquakes are so small in magnitude that we can't feel them. The United States Geological Survey only records about 20 each year in the US. The reason earthquakes happen in the first place has to do with the tectonic plates below the surface of the earth. Tectonic plates move around constantly. Those movements cause tension, which in turn causes huge faults or cracks in the rocks. The faults sometimes get stuck, and when they get unstuck, they cause an earthquake! Tectonic plates move in three ways: subduction, lateral sliding, and spreading. The closer you are to an earthquake's epicenter, the more strongly you will feel it. This is because an earthquake loses its intensity as it travels away from the epicenter. Scientists measure the intensity of an earthquake using a seismograph, which detects and measures the vibrations of the earthquake. The magnitude of the earthquake is the number we assign to record its size. A magnitude of 5.5 if considered moderate. Above 8.0 means it's a major earthquake. And earthquakes with a magnitude of 2.5 or lower are usually not felt at all.
- #8: A fault is a weak point in the tectonic plate where the pressure inside the crust is released. The area inside the Earth where an earthquake starts is known as the focal point of the quake or the focus. It is centered on the portion of the fault that has the greatest movement. The point at the Earth's surface directly above the focus is known as the epicenter of the quake. During an earthquake, the strongest shaking occurs at the epicenter. Sometimes, the ground surface breaks along the fault. There are also times the movement is deep underground and the surface does not break. Scientists often name an earthquake after the region that is closest to its epicenter. Generally, if two earthquakes of equal strength originate from the same epicenter, the one with the shallower focus causes more destruction. Seismic waves from a deep-focus earthquake lose more of their energy as they travel farther up to surface.
- #10: What is continental crust?oceanic crust?
- #11: How do seismologist measure the epicenter or locate the epicenter of an earthquake…
- #17: Write the sample computation…
- #18: SAY AFTER THE ACTIVITY Now that you have completed answering the activity, you have discovered and revealed to yourself how seismologists use the data from the three seismic stations to locate the epicenter of an earthquake. In this activity always remember that they use the triangulation method because the hypothetical earthquake happens locally that is why they used the formula stated in the procedure. The distances of the P-waves and S-waves are not in greater distances. You have already understood how seismologists gather data and determine earthquakes’ epicenter.