Group 6 Earthquake Measurement and Location PDF

**Technological University of the Philippines** College of Engineering Department of Civil Engineering **PCS 2- Earthquake Engineering** **Written Report** **(Earthquakes: Measurement and Location)** Submitted to: **Engr. Edmundo Dela Cruz** **EARTHQUAKES: MEASUREMENT AN...

**Technological University of the Philippines** College of Engineering Department of Civil Engineering **PCS 2- Earthquake Engineering** **Written Report** **(Earthquakes: Measurement and Location)** Submitted to: **Engr. Edmundo Dela Cruz** **EARTHQUAKES: MEASUREMENT AND LOCATION** ***INTRODUCTION*** According to Earthquakelist.org, In the last ten years, 7,689 earthquakes of magnitude four or higher have struck within 300 kilometers (186 miles) of The Philippines. This equates to an annual average of 768 earthquakes, or 64 per month. Every 11 hours, an earthquake will strike near the Philippines. In 2023 alone, there were 1,400 earthquakes recorded, having 7.6 magnitude as the strongest. This 7.6 magnitude earthquake occurred last December 02, 2023. It was located 177 kilometers (110 miles) north-northeast of Davao having a depth of 51 kilometers. The strongest earthquake recorded since 1900 was during the General Santos earthquake, registering an 8.3 magnitude earthquake on August 15, 1918. While that earthquake was strong, the strongest and deadliest earthquake recorded was the Moro Gulf Earthquake in 1976. It was an 8.1 magnitude earthquake that resulted in a 9-meter-high tsunami off the shores of Sultan Kudarat where an estimated 8,000 casualties and 90,000 people were left homeless after the wipeout. After that earthquake, the late President Marcos Sr. ordered the revision of the provisions of the National Building Code, requiring structures to withstand an Intensity 8 earthquake. *Figure 1. Yearly Earthquakes within 300 km (186 mi) of The Philippines with a magnitude of 4 or above.* In the last ten years, 992 earthquakes of magnitude four or higher have struck within 300 kilometers (186 miles) of National Capital Region, The Philippines. This equates to an annual average of 99 earthquakes, or 8 per month. Every three days, an earthquake will strike near the National Capital Region. The strongest earthquake recorded in Metro Manila over the last 10 years happened on July 24,2021 with a magnitude of 6.7. It struck 87 kilometers (54 miles) south-southwest of  [Las Piñas](https://earthquakelist.org/philippines/national-capital-region/las-pinas/) City having a depth of 110 kilometers. The strongest earthquake recorded since 1990 occurred on July 16,1990 located 115 kilometers (71 miles) south-southwest of Quezon City.  *Figure 2. Yearly Earthquakes within 300 km (186 mi) of National Capital Region with a magnitude of 4 or above.* In an earthquake, the movement of one block of rock over another generates energy that causes the ground to vibrate. That vibration pushes the adjacent piece of ground, causing it to tremble, and thus the energy flows out in a wave from the earthquake hypocenter. A seismographic network records earthquake. Each seismic station in the network records ground movement at that location. The most essential earthquake measures are based on two different perspectives: magnitude and intensity. An earthquake, according to experts, is an event that occurs within the earth. To the rest of us, it\'s an extraordinary ground movement. The former is measured by magnitude, whereas the latter is measured by intensity. ***\ MEASURING EARTHQUAKES*** Two different viewpoints underpin the most important measurements related to earthquakes: magnitude and intensity. To scientists, an earthquake is an event inside the earth. To the rest of us, it is an extraordinary movement of the ground. Magnitude measures the former, while intensity measures the latter. ***MAGNITUDE*** **What is magnitude?** Magnitude describes the overall size of an earthquake as an event in the earth. Magnitude represents the total energy the earthquake radiates, and is calculated using information on how large an area moves, the distance that one side of the fault moves past the other, and the rigidity of the rock. The international standard for measuring earthquake magnitude is called the moment magnitude scale and was formulated by Caltech seismologist Hiroo Kanamori with alumnus Thomas Hanks. Caltech\'s Charles Richter conceptualized magnitude. He developed a method to numerically report the relative sizes of earthquakes before earthquake magnitude could be measured directly. He described the first magnitude scale, which came to be known as the Richter scale, in a paper published in 1935. **How is magnitude measured?** Magnitude is estimated using data from multiple seismograms. Estimates are made by calculating the total energy from the rupture area times the average movement on the fault. These factors can be reconstructed from seismograms or measured directly in the field by geologists, which makes the moment magnitude scale the first based on measurable physical factors. An important piece of information to keep in mind is that the magnitude scale is logarithmic. In other words, it is "comparing amplitudes of waves on a seismogram, not the strength, or energy, of the quakes," according to USGS. This helps us understand that while the size (amplitude) differences between small and big quakes are big enough, it is the strength (energy) differences that are meaningful. Try out USGS's "How Much Bigger...?" calculator to learn more about how to measure the magnitude of an earthquake. ***The Richter Scale*** From 1935 until 1970, the earthquake magnitude scale was the Richter scale, a mathematical formula invented by Caltech seismologist Charles Richter to compare quake sizes. The Richter Scale was replaced because it worked largely for earthquakes in Southern California, and only those occurring within about 370 miles of seismometers. In addition, the scale was calculated for only one type of earthquake wave. It was replaced with the Moment Magnitude Scale, which records all the different seismic waves from an earthquake to seismographs across the world. ***Richter\'s equations are still used for forecasting future earthquakes and calculating earthquake hazards.*** ***Figure 4.** Average Earthquake Effects of Earthquake Magnitudes* ***Moment Magnitude Scale*** Today, earthquake magnitude measurement is based on the Moment Magnitude Scale (MMS). MMS measures the movement of rock along the fault. It accurately measures larger earthquakes, which can last for minutes, affect a much larger area, and cause more damage. The Moment Magnitude can measure the local Richter magnitude (ML), body wave magnitude (Mb), and surface wave magnitude (Ms). The moment magnitude scale (MMS; denoted explicitly with M or M~w~  or M~wg~, and generally implied with use of a single M for magnitude) is a measure of an earthquake\'s magnitude (\"size\" or strength) based on its seismic moment. M~w~ was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. ***Earthquake Magnitude Classes*** Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude. What's the difference between a light and moderate quake? These terms are magnitude classes. Classes also provide earthquake measurement. The classification starts with "minor" for magnitudes between 3.0 and 3.9, where earthquakes generally begin to be felt, and ends with "great" for magnitudes greater than 8.0, where significant damage is expected. ***Figure 5.** Earthquake Magnitude Classes* **INTENSITY** The effect of an earthquake on the Earth\'s surface is called the intensity. The intensity is generally higher near the ***epicenter***. It is represented by Roman Numerals (I, II, III, IV, V, VI, VII, VIII, IX, and X) depending on descriptions of each intensity level that based on observed damage to structures, impact on people, and the overall felt experience. In the Philippines the intensity of an earthquake is determined using the **PHIVOLCS Earthquake Intensity Scale (PEIS)** - a measure of how an earthquake is felt in a certain area, based on the relative effects of an earthquake on structures and surroundings. The assessment of earthquake intensity employs two scales: the ***Modified Mercalli Intensity (MMI)*** ***scale*** and the ***European Macroseismic Scale (EMS)***. With comparable intensity levels and descriptions, these scales are essential tools for understanding the local impact of earthquakes. Seismic intensity scales categorize the intensity or severity of ground shaking at a given location, such as resulting from an earthquake. They are distinguished from seismic magnitude scales, which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking. They are crucial in evaluating seismic events, managing emergencies, increasing public awareness, and strengthening infrastructure resilience in their respective regions. Additionally, the intensity scale encompasses specific key responses, including people waking, furniture movement, chimney damage, and ultimately, complete destruction. **TWO SCALE MEASUREMENT OF EARTHQUAKE INTENSITY** a. **Modified Mercalli Intensity (MMI) scale** ***Figure 6. Modified Mercalli Intensity*** The lower numbers of the intensity scale generally deal with how the earthquake is felt by people. The higher numbers on the scale are based on observed structural damage. Structural engineers usually contribute information for assigning intensity values of VIII or above. b. **European Macroseismic Scale (EMS)** *Figure 7. European Macroseismic Scale* **Comparison of Two Intensity Scales** **1. Origin and Development** **2.** **Scale Range:** **3.** **Descriptors and Descriptions:** ***LOCATING EARTHQUAKES*** A. ***Seismic Waves*** ***When an earthquake occurs, it releases energy in the form of seismic waves. The shaking phenomenon being felt during an earthquake and the damage it could cause can be explained by these waves. They can travel through and around earth and can be recorded through seismographs. Seismic waves are divided into two major classifications: the body waves and surface waves. They are categorized according to where they travel and how they move particles.*** ***Figure 8. Body waves (P and S-waves) and Surface waves*** i. ***Body waves*** a. ***P-waves*** b. ***S-waves*** ii. ***Surface waves*** a. ***Love waves*** b. ***Rayleigh waves*** B. ***Triangulation Method*** **Two steps in locating an earthquake using Triangulation Method:** 1. ***Measure: Measure the time between the arrival of the P wave and the arrival of the S wave (S-P time) at each station.*** 2. ***Locate: On a map, mark each station and draw a circle around the station with a radius*** ***equal to its distance from the earthquake. The earthquake occurred at the point where all three circles intersect.***  ***TECHNOLOGICAL EARTHQUAKE ADVANCEMENTS IN THE PHILIPPINES*** 1. **The Universal Structural Health Evaluation and Recording System (USHER)** USHER is a monitoring system composed of an advanced accelerometer, a web portal system, and a mobile application designed to produce a building structural health assessment that can be used 24 hours a day, 7 days a week. USHER was developed by Dr. Francis Aldrine A. Uy of USHER Technologies. USHER Technologies is a company funded by the Department of Science and Technology and launched by Mapua University in 2019. USHER is used for earthquake detection and early warning. It won the 2023 Innovation Awards and was granted a 1-million-peso funding for further research. This technology promotes both resiliency and safety of the structures amid destructive earthquakes. 2. **Google Earthquake Alert System** The Android Earthquake Alerts System is a free service that detects earthquakes all over the world and alerts Android users before the shaking begins. All cellphones have tiny accelerometers that can detect tremors and speed, both of which suggest the possibility of an earthquake. If the phone senses an earthquake, it transmits a signal to Google earthquake detection server, along with a rough position of where the shaking happened. The server then integrates data from multiple phones to determine whether an earthquake is occurring.  3. **How Safe Is My House? Self-check for Earthquake Safety of Concrete Hollow Blocks (CHB) Houses in the Philippines** This mobile application was launched by the Department of Science and Technology- Philippine Institute of Volcanology and Seismology on April 13, 2021. It is a basic and straightforward tool for owners and occupants of residential homes and other 1-2-level CHB structures. Android users can analyze the safety of their CHB houses and discover their likely vulnerability to a major earthquake by answering 12 questions. The outcome establishes if the structure is safe and, presumably, was created by standard construction practices. If not, it may suggest additional professional consultations and structural strengthening. *Figure 18. 12 Basic Questions in How Safe is My House? Mobile Application* 4. **HazardHunterPH** HazardHunterPH is a one-stop shop for hazard assessment services in the Philippines. It enables the user to generate hazards assessment reports for the user\'s chosen site fast and efficiently. It was developed by GeoRisk Philippines, which is a a collaborative program led by DOST-PHIVOLCS and involving DOST-PAGASA, DOST-ASTI, DENR-MGB, DENR-NAMRIA, DND-OCD, DepEd, DOH, NHMFC, and SHFC. With all its features now available on mobile devices, it makes danger assessment portable and accessible 24 hours a day, seven days a week. It serves as a quick reference for property owners, buyers, land developers, planners, local governments, and other stakeholders who require immediate risk information and evaluation. Its goal is to raise public awareness about natural disasters and advocate for the execution of strategies to prepare for and minimize the effects of disasters.  *Figure 19. HazardHunterPH web interface* **Core features of HazardHunterPH Mobile:** - Find out if a location is safe or prone to seismic, volcanic, or hydro-meteorological hazards - Generate hazard assessment reports with explanations and recommendations - See which areas in the Philippines are prone to different hazards - Display exposure of schools, hospitals, and roads to various hazards - View up-to-date hazard and risk information from mandated government agencies *Figure 20. Sample of HunterHazardPH Seismic Report with Recommendation* ***References:*** British Geological Survey. (n.d.). How are earthquakes detected, located, and measured?. Retrieved from [https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/how-are-earthquakes-dete cted/](https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/how-are-earthquakes-dete%20cted/). Daniels, K.S. & Solada, K. (2021). Measuring Earthquakes. 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Different Types of Seismic Wave. Retrieved from. Philstar GLOBAL (2022). Kawakin Core-Tech introduces 'Total Solutions' to earthquake disasters, enters PHIVOLCS. DOST PHIVOLCS releases HazardHunterPH Mobile App for IOS. Retrieved from [DOST-PHIVOLCS RELEASES HAZARDHUNTERPH MOBILE APP FOR iOS](https://www.phivolcs.dost.gov.ph/index.php/news/13065-dost-phivolcs-releases-hazardhunterph-mobile-app-for-ios) ***PHIVOLCS. Introduction to Earthquake. Retrieved from*** [***https://www.phivolcs.dost.gov.ph/index.php/earthquake/introduction-to-earthquake***](https://www.phivolcs.dost.gov.ph/index.php/earthquake/introduction-to-earthquake) PHIVOLCS. Technological Innovations for Earthquake Reduction. Retrived from Quadra-Balibay A. (2023) First Filipino-made monitoring system for earthquake wins 1M grant. Tijs,D. (2024) National Capital Region Earthquake Report. Retrieved from [The complete Philippines earthquake report (up-to-date 2024). (earthquakelist.org)](https://earthquakelist.org/philippines/#:~:text=A%20total%20of%207671%20earthquakes%20with%20a%20magnitude,hit%20near%20The%20Philippines%20roughly%20every%2011%20hours.) Tijs,D. (2024) The Philipppines Earthquake Report. Retrieved from The Iris Consortium. (n.d.). How are earthquakes located?. Retrieved from [https://www.iris.edu/hq/files/pu blications/brochures\_onepagers/doc/OnePager6.pdf](https://www.iris.edu/hq/files/pu%20blications/brochures_onepagers/doc/OnePager6.pdf). United States Geological Survey: Earthquake Hazards Program. (n.d.). The Science of Earthquakes. https:// www.usgs.gov/programs/earthquake-hazards/science-earthquakes\#:\~:text=The%20energy%20rad iates%20outward%20from,like%20our%20houses%20and%20us!. United States Geological Survey. (n.d.). Body waves inside the earth. Retrieved from https://earthquake.usg s.gov/earthquakes/events/1906calif/18april/earthwaves.php. USGS. Science for a changing world. The Modified Mercalli Intensity Scale. 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