Earthquake_Chapter 1 to 3_Handouts for Students.pdf

CHAPTER 1 INTRODUCTION TO EARTHQUAKE ENGINEERING Earthquake Engineering is a specialized branch of civil engineering that focuses on analyzing and designing structures to withstand seismic fo...

CHAPTER 1 INTRODUCTION TO EARTHQUAKE ENGINEERING Earthquake Engineering is a specialized branch of civil engineering that focuses on analyzing and designing structures to withstand seismic forces. The primary objective of earthquake engineering is to protect human life, minimize damage to structures, and ensure that buildings and infrastructure remain functional after an earthquake. Key goals of earthquake engineering include: Y 1. Seismic Hazard Analysis: Understanding the probability and intensity of earthquakes in a particular region. This involves P studying the history of seismic activity, fault lines, and geological conditions. 2. O Seismic Design and Retrofitting: Developing design criteria and structural systems that can absorb and dissipate seismic energy. This includes using flexible materials, base isolators, and energy-dissipating devices. C 3. Post-Earthquake Evaluation: Assessing the safety and stability of structures after an earthquake to determine if they can be used safely or if they need repairs or demolition. T N 4. Building Codes and Standards: Creating and enforcing regulations that ensure all new constructions are designed to withstand seismic forces. These codes are regularly updated based on new research and technological advancements. E What is an earthquake? D An earthquake is a weak to violent shaking of the ground produced by the sudden movement of rock materials below the earth’s surface. U The earthquakes originate in tectonic plate boundary. The focus is point inside the earth where the earthquake started, sometimes called the hypocenter, and the point on the surface of the earth directly above the focus is called the epicenter. T S Why Earthquakes Occur According to Federal Emergency Management Agency (FEMA), an earthquake is ground shaking caused by a sudden movement of rock in the earth’s crust. Such movements occur along faults, which are thin zones of crushed rock separating blocks of crust. When one block suddenly slips and moves relative to the other along a fault, the energy released creates vibrations called seismic waves that radiate up through the crust to the earth’s surface, causing the ground to shake. (Note: FEMA is a United States government agency with the purpose to coordinate aid and respond to disasters around the nation when local resources are insufficient.) De nition of Terms in Earthquake Engineering 1. Seismic Waves: Vibrations that propagate through the Earth's crust during an earthquake. They are classified into: ◦ P-waves (Primary waves): The fastest seismic waves, which compress and expand the material they move through. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 1 of 22 fi  ◦ Surface waves: Travel along the Earth's surface and tend to cause the most destruction. 2. Magnitude: A measure of the total energy released by an earthquake, commonly measured using the Richter scale or the moment magnitude scale (Mw). 3. Epicenter: The point on the Earth's surface directly above the earthquake’s hypocenter. 4. Hypocenter (Focus): The actual location within the Earth where the earthquake begins. 5. Fault: A fracture in the Earth's crust where blocks of the crust have moved relative to each other. Earthquakes commonly occur along faults. Y P 6. Liquefaction: A process where saturated soil temporarily loses its strength and behaves like a liquid due to intense shaking during an earthquake. 7. O Base Isolation: A technique in seismic design that involves installing bearings or isolators between the building and its C foundation to reduce the transmission of ground motion. 8. Damping: The process of reducing the amplitude of vibrations in a structure. Devices such as dampers absorb and dissipate T seismic energy. N 9. Seismic Zoning: Dividing regions into zones based on their seismic hazard levels to inform building codes and construction practices. E 10. Retrofitting: The process of strengthening existing structures to make them more resistant to seismic forces. D U History of Philippine Earthquakes T Philippines is one of the seismically active countries in the world where it is located in the pacific ring of fire. USGS defines it as the most earthquakes and volcanic eruptions do not strike randomly but occur in specific areas, such as along plate boundaries. One such S area is the circum-Pacific Ring of Fire, where the Pacific Plate meets many surrounding plates. The Ring of Fire is the most seismically and volcanically active zone in the world. 1968 August 02 Casiguran Earthquake According to PHIVOLCS, at 4:19 AM (local time) on August 02, 1968 an earthquake with an intensity of VIII in the Rossi-Forel Intensity Scale rocked the town of Casiguran, Aurora. This was considered the most severe and destructive earthquake experienced in the Philippines during the last 20 years. Two hundred seventy (270) persons were killed and 261 were injured as a result of the earthquake. A six-storey building in Binondo, (Ruby Tower) Manila collapsed instantly during the quake while several major buildings near Binondo and Escolta area in Manila sustained varying levels of structural damages. The cost of property damage was several million dollars. Extensive landslides and large fissures were observed in the mountainous part of the epicentral area. Tsunami was also observed and recorded as far as observation in tide gauge station in Japan. Date of Event August 02, 1968 Origin Time 4:19 am (20:19 GMT) Epicenter 16.3 N Latitude 122.11 E Longitude or approximately CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 2 of 22 Depth approximately 31 km from the surface. Intensity Report: Intensity VIII Casiguran, Quezon Intensity VII Manila and Palanan Intensity VI Baler, Quezon City, Tuguegarao, Aparri, Baguio, Dagupan, Iba, Cabanatuan, Alabat, Intensity V Tarlac, Ambulong, Infanta, Jomalig Intensity IV Legaspi, Lucena, Calapan, Aurora, Laoag, Catarman, Virac Intensity III Romblon, Vigan Note: Intensity scale used in these observations was the Adapted Rossi-Forel Earthquake Intensity Scale of I-IX. Summary of Damages: Y Damage to Particular Buildings in Manila P The severe damage area was concentrated in a relatively small part of Greater Manila. This part of Manila lies in the mouth of Pasig O River (a major river system in Metro Manila) and includes the deepest and most recent alluvial deposits in the city. C Ruby Tower The Ruby Tower was a large six-storey building containing 38 commercial units in its first two floors and 76 residential units in its upper T four floors. Most of the building collapsed except for a part of the northern end of first and second floors (Photo 1 & 2), killing 268 persons and injuring 260 of the occupants. N E D U T S A six-storey building in Binondo, (Ruby Tower) Manila collapsed instantly during the Casiguran Earthquak on August 2, 1968. Examples of Destructive Earthquake Events International Examples: 1. Great East Japan Earthquake (2011) ◦ Magnitude: 9.0 ◦ Location: Tōhoku region, Japan ◦ Impact: Triggered a devastating tsunami, causing over 15,000 deaths and the Fukushima nuclear disaster. It also caused significant damage to school buildings, with several being destroyed or severely damaged. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 3 of 22  2. Sichuan Earthquake (2008) ◦ Magnitude: 7.9 ◦ Location: Sichuan Province, China ◦ Impact: The earthquake caused the collapse of thousands of buildings, including many school buildings. The collapse of Juyuan Middle School resulted in the deaths of around 900 students. ◦ Casualties: Approximately 87,000 dead, including thousands of schoolchildren. 3. Haiti Earthquake (2010) ◦ Magnitude: 7.0 ◦ Location: Near Port-au-Prince, Haiti Y ◦ Impact: Widespread destruction, with numerous schools collapsing, such as the St. Gérard School, where dozens of children died. P ◦ Casualties: Around 230,000 dead, including hundreds of schoolchildren. Philippine Examples: O C 1. Luzon Earthquake (1990) ◦ Magnitude: 7.8 T ◦ Location: Central Luzon, Philippines N ◦ Impact: Widespread destruction in Baguio City, including the collapse of multiple school buildings such as the University of Baguio. E ◦ Casualties: Over 1,600 dead, including students and teachers. D 2. Bohol Earthquake (2013) ◦ Magnitude: 7.2 U ◦ Location: Bohol, Philippines T ◦ Impact: Significant damage to infrastructure, including the collapse of school buildings. The collapse of public schools such as Loon National High School was reported. S ◦ Casualties: Over 200 dead. 3. Mindanao Earthquakes (2019) ◦ Magnitude: Series of earthquakes, the strongest being 6.9 ◦ Location: Mindanao, Philippines ◦ Impact: Severe damage to buildings, including several schools in Cotabato and Davao del Sur. The Makilala Central Elementary School, for example, suffered significant damage. ◦ Casualties: Around 21 dead, with several injuries reported among students. References 1. Bolt, B. A. (1999). Earthquakes (4th ed.). W.H. Freeman and Company. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 4 of 22  3. National Institute of Building Sciences. (2021). Designing for Earthquakes: A Manual for Architects (FEMA P-454). Federal Emergency Management Agency (FEMA). https://www.fema.gov 4. Ranjan, G., & Rao, A. S. R. (2000). Basic and Applied Soil Mechanics (2nd ed.). New Age International Publishers. 5. U.S. Geological Survey (USGS). (2012). The Tōhoku Earthquake and Tsunami of March 11, 2011. Earthquake Hazards Program. https://earthquake.usgs.gov/earthquakes/events/2011 6. Department of Science and Technology - Philippine Institute of Volcanology and Seismology (DOST-PHIVOLCS). (2013). Bohol Earthquake 2013: A Final Report. PHIVOLCS Earthquake Reports. http://www.phivolcs.dost.gov.ph Elnashai, A. S., & Sarno, L. D. (2008). Fundamentals of Earthquake Engineering. John Wiley & Sons. Y 7. P 8. International Federation of Red Cross and Red Crescent Societies (IFRC). (2010). Haiti earthquake: An IFRC response operation. IFRC Disaster Reports. https://www.ifrc.org 9. O United Nations Educational, Scientific and Cultural Organization (UNESCO). (2011). Education for All Global Monitoring Report C 2011: The hidden crisis—Armed conflict and education. UNESCO Publishing. 10. Zheng, Y., & Zhen, W. (2013). School construction and safety in earthquake-prone regions of China: Lessons from the 2008 T Sichuan earthquake. International Journal of Disaster Risk Reduction, 6(1), 47-61. N E Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS) D The Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS) is a comprehensive assessment conducted to understand the potential impact of a large earthquake on Metro Manila, the capital region of the Philippines. The study was initiated in response to the growing concerns about the seismic vulnerability of the region, particularly due to the presence of the West Valley Fault, a major U fault line that runs through Metro Manila and nearby provinces. T Objectives of the MMEIRS S The main objectives of the MMEIRS were: 1. Hazard Assessment: To identify and map out areas in Metro Manila that are highly vulnerable to seismic activity. This includes understanding the possible ground shaking, liquefaction, and landslide risks. 2. Impact Estimation: To estimate the potential damage and casualties that could result from a major earthquake, particularly one with a magnitude similar to historical significant events. 3. Mitigation Strategies: To develop and recommend strategies for reducing the impact of such an earthquake. This includes suggestions for improving building codes, retrofitting existing structures, and enhancing emergency preparedness and response capabilities. 4. Public Awareness: To raise awareness among residents, local governments, and stakeholders about the risks and necessary preparations for a large earthquake. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 5 of 22  1. Seismic Vulnerability: The study identified that Metro Manila is highly vulnerable to earthquakes due to its dense population, old and poorly constructed buildings, and the presence of critical infrastructure along fault lines. The West Valley Fault is particularly concerning because it is capable of producing a magnitude 7.2 earthquake. 2. Potential Impact: A magnitude 7.2 earthquake on the West Valley Fault could result in massive destruction, with estimates suggesting that around 40% of residential buildings could be heavily damaged, and tens of thousands of casualties could occur. Infrastructure such as roads, bridges, and utilities could be severely affected, leading to widespread disruption. 3. Risk Zones: The study mapped out areas in Metro Manila based on their level of risk. Areas along the West Valley Fault, such as Quezon City, Marikina, and Pasig, were identified as high-risk zones. Liquefaction-prone areas, such as those near rivers and reclaimed land, were also highlighted. Y Recommendations from the MMEIRS P 1. Strengthening Building Codes: The study recommended updating and strictly enforcing building codes to ensure that new O structures are earthquake-resistant. Retrofitting existing buildings, especially schools, hospitals, and other critical infrastructure, was also emphasized. C 2. Disaster Preparedness: Enhancing disaster preparedness at all levels, including government agencies, businesses, communities, and individuals, was a key recommendation. This involves regular earthquake drills, improving early warning T systems, and ensuring that emergency services are well-equipped and trained. N 3. Land Use Planning: The study advised on better land use planning to avoid constructing critical infrastructure and residential areas in high-risk zones. It also suggested relocating vulnerable populations where feasible. E 4. Public Awareness Campaigns: Raising awareness about earthquake risks and preparation was highlighted as essential. The D study recommended ongoing public education campaigns to ensure that residents know how to prepare for and respond to an earthquake. U T Preparation for Students S Given the risks identified by the MMEIRS, it is crucial that students in Metro Manila are well-prepared for a potential earthquake. Here are some key preparation steps for students: 1. Participate in Earthquake Drills: Schools should regularly conduct earthquake drills to familiarize students with the procedures during an earthquake. Students should know the “Drop, Cover, and Hold On” method to protect themselves from falling debris. 2. Emergency Kits: Students should have access to emergency kits that include basic supplies like water, food, first aid items, and a flashlight. Schools should ensure that classrooms are equipped with these kits. 3. Awareness and Education: Students should be educated about the risks of earthquakes, the importance of staying calm during an event, and the proper actions to take before, during, and after an earthquake. This includes knowing evacuation routes and safe spots in classrooms and buildings. 4. Family Emergency Plan: Students should work with their families to create an emergency plan. This plan should include a designated meeting place in case family members are separated during an earthquake, emergency contact numbers, and a strategy for how to communicate if phone lines are down. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 6 of 22  6. Mental Preparedness: Preparing students mentally is just as important as physical preparations. Schools should provide information and workshops on how to deal with the psychological impact of earthquakes, including managing fear and anxiety. References: 1. Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS). (2004). Final Report: Main Study (Volume I). Japan International Cooperation Agency (JICA), Philippine Institute of Volcanology and Seismology (PHIVOLCS), and Metropolitan Manila Development Authority (MMDA). Y 2. Japan International Cooperation Agency (JICA). (2004). Metro Manila Earthquake Impact Reduction Study (MMEIRS). Retrieved from https://www.jica.go.jp/english/our_work/thematic_issues/disaster/case.html P 3. Philippine Institute of Volcanology and Seismology (PHIVOLCS). (2004). West Valley Fault System and Earthquake O Preparedness. Retrieved from https://www.phivolcs.dost.gov.ph 4. C Metropolitan Manila Development Authority (MMDA). (2004). Earthquake Preparedness in Metro Manila: Lessons from the MMEIRS Study. Retrieved from https://www.mmda.gov.ph T 5. U.S. Geological Survey (USGS). (2021). Earthquake Preparedness for Schools and Students. Retrieved from https:// www.usgs.gov/natural-hazards/earthquake-hazards/earthquake-preparedness N E Earthquake preparedness D Preparing for an earthquake involves taking steps to ensure safety, minimize damage, and increase the chances of survival during and after the event. Here are some key earthquake preparedness activities: U 1. Create an Emergency Plan: T Family Communication Plan: Develop a plan for how family members will communicate during and after an earthquake if S separated. Choose an out-of-area contact person who everyone can reach. Emergency Meeting Spots: Identify safe spots in your home (e.g., under sturdy furniture) and outside locations where family members can meet after the quake. 2. Assemble an Emergency Kit: Essentials: Include items such as water (at least three days’ supply for each person), non-perishable food, a first-aid kit, flashlights, batteries, a whistle, dust masks, and sanitation supplies. Personal Items: Include medications, important documents, cash, and items specific to your family’s needs (e.g., baby supplies, pet food). 3. Secure Your Home: CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 7 of 22  Hazardous Items: Store heavy and breakable items on lower shelves. Ensure that chemicals and flammable liquids are stored securely. Structural Safety: If you live in an earthquake-prone area, consider a professional inspection to assess your home’s structural integrity. Retrofit older buildings to make them more resistant to seismic activity. 4. Practice Earthquake Drills: Drop, Cover, and Hold On: Regularly practice the “Drop, Cover, and Hold On” procedure with your family or household members. This involves dropping to your hands and knees, covering your head and neck under a sturdy piece of furniture or against an interior wall, and holding on until the shaking stops. Y Evacuation Routes: Identify and practice evacuation routes from your home, workplace, or school. Ensure everyone knows the P quickest and safest way to exit the building if necessary. 5. Know How to Turn Off Utilities: O C Gas: Learn how to shut off the gas supply at the main valve. Only turn it off if you smell gas or suspect a leak. T Electricity: Know how to turn off the electrical power at the main circuit breaker to prevent electrical fires. N Water: Familiarize yourself with how to turn off the water supply to prevent flooding from broken pipes. E 6. Stay Informed: D Earthquake Alerts: Sign up for local earthquake alerts and warnings. Have a battery-operated or hand-crank radio to receive emergency information if power is out. U Learn About Local Risks: Understand the earthquake risks specific to your area, including the types of faults nearby and the T history of seismic activity. S 7. Educate and Involve the Community: Community Drills: Participate in or organize community earthquake drills. This helps build a collective awareness and preparedness. Workshops and Training: Attend or host workshops on earthquake preparedness, first aid, and disaster response. Educating others in the community increases overall resilience. 8. Review Insurance Coverage: Earthquake Insurance: Check if your homeowner's or renter's insurance policy covers earthquake damage. Consider purchasing additional earthquake insurance if you live in a high-risk area. 9. Prepare Your Workplace and School: CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 8 of 22  School: If you have children, understand their school’s earthquake preparedness plan. Make sure your child knows what to do during an earthquake. 10. Prepare for Aftershocks: Immediate Safety: After an earthquake, be prepared for aftershocks, which can occur minutes, days, or even months later. Stay vigilant and avoid areas that could become hazardous. Check for Hazards: After the shaking stops, check your home for hazards such as gas leaks, damaged electrical wiring, and structural damage. Y Situational Interaction Questions with Answers: Introduction to Earthquake Engineering P 1. Scenario: Understanding Seismic Hazards O Question: What are seismic hazards, and why are they important in civil engineering? 2. Scenario: Seismic Waves and Building Response C Question: Describe how seismic waves affect buildings and structures during an earthquake. 3. Scenario: Importance of Building Codes T Question: Why are building codes important in earthquake-prone regions? N 4. Scenario: Seismic Retrofitting E Question: What is seismic retrofitting, and why is it necessary for existing buildings? D 5. Scenario: Design Considerations Question: What factors do engineers consider when designing earthquake-resistant buildings?6. Scenario: Community U Resilience Question: How can earthquake engineering contribute to community resilience? T 7. Scenario: Role of Engineers in Earthquake Preparedness S Question: What is the role of civil engineers in earthquake preparedness and response? CHAPTER 2 CAUSES OF EARTHQUAKES AND FAULTING; TECTONIC PLATES; SEISMIC ZONES OF THE PHILIPPINES Causes of Earthquakes and Faulting 1. Tectonic Activity: CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 9 of 22  ◦ The Earth's lithosphere is divided into several tectonic plates that are constantly moving, albeit very slowly. These plates can move toward each other (convergent boundaries), away from each other (divergent boundaries), or slide past each other (transform boundaries). The friction between these plates prevents them from sliding smoothly, causing stress to build up over time. When the stress exceeds the frictional forces, it is released as an earthquake. ◦ Example in the Philippines: The Philippine Sea Plate and the Eurasian Plate interact along the Philippine Trench and the Manila Trench, leading to frequent seismic activity. 2. Volcanic Activity: Y ◦ Earthquakes can also be caused by volcanic activity. As magma moves beneath the Earth’s crust, it can cause the surrounding rock to crack and produce an earthquake. These earthquakes are typically smaller in magnitude but can be P a precursor to a volcanic eruption. O ◦ Example in the Philippines: The Pinatubo earthquake in 1991 was associated with the volcanic eruption of Mount Pinatubo. C The Philippine Institute of Volcanology and Seismology classifies volcanoes according to its eruptive history T Erupted within historical times (within the last 600 years), accounts of these eruptions were documented by man erupted within the last 10,000 years based on the analyses of material from young volcanic deposits. N Name of Item No. Latitude Longitude Province E Volcano Babuyan Island Group, Cagayan D 1 Babuyan Claro 19.52408 121.95005 in Luzon Boundaries of Laguna and U 2 Banahaw 14.06038 121.48803 Quezon in Luzon 3 Biliran (Anas) 11.63268 124.47162 Leyte in Visayas T 4 Bud Dajo 6.01295 121.05772 Sulu in Mindanao S 5 Bulusan 12.76853 124.05445 Sorsogon, Bicol Region in Luzon 6 Cabalian 10.27986 125.21598 Southern Leyte in Visayas 7 Cagua 18.22116 122.1163 Cagayan in Luzon Camiguin de Babuyan Island Group, Cagayan 8 18.83037 121.86280 Babuyanes in Luzon Babuyan Island Group, Cagayan 9 Didicas 19.07533 122.20147 in Luzon 10 Hibok-hibok 9.20427 124.67115 Camiguin in Mindanao 11 Iraya 20.46669 122.01078 Batan Island, Batanes in Luzon 12 Iriga 13.45606 123.45479 Camarines Sur in Luzon 13 Isarog 13.65685 123.38087 Camarines Sur in Luzon 14 Kanlaon 10.41129 123.13243 Negros Oriental CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 10 of 22  Leonard 15 7.39359 126.06418 Davao del Norte Kniaseff 16 Makaturing 7.64371 124.31718 Lanao del Sur 17 Matutum 6.36111 125.07603 Cotobato in Mindanao 18 Mayon 13.25519 123.68615 Albay, Bicol Region in Luzon Musuan 19 7.87680 125.06985 Bukidnon in Mindanao (Calayo) South Cotobato/General Santos/ 20 Parker 6.10274 124.88879 North Cotabato/Sarangani Provinces in Mindanao Boundaries of Pampanga, Tarlac 21 Pinatubo 15.14162 120.35084 and Zambales in Luzon Lanao del Sur and Cotobato in Y 22 Ragang 7.69066 124.50639 Mindanao Babuyan Island Group, Cagayan P 23 Smith 19.53915 121.91367 in Luzon O 24 Taal 14.01024 120.99812 C Batangas in Luzon 3. Human Activity: T ◦ Activities such as mining, reservoir-induced seismicity (due to large dams), geothermal energy extraction, and hydraulic N fracturing (fracking) can induce earthquakes. These are generally smaller in magnitude but can be significant depending on the region. E 4. Faulting: D ◦ Earthquakes can occur when stress on a fault line becomes so great that the rocks on either side of the fault suddenly U slip. This slip causes seismic waves that propagate through the Earth, causing an earthquake. T S According to PHIVOLCS, there are five major active fault lines in the country, namely: 1. Marikina Valley Fault 2. Western Philippine Fault 3. Eastern Philippine Fault 4. Southern of Mindanao Fault CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 11 of 22 Faulting: ◦ A fault is a fracture or zone of fractures in the Earth's crust along which there has been displacement of the sides relative to one another parallel to the fracture. Faults are classified based on the direction of movement: normal faults, reverse faults, and strike-slip faults. ◦ Normal Faults occur where the crust is being extended. ◦ Reverse Faults occur where the crust is being compressed. Y ◦ Strike-Slip Faults occur where the crustal blocks move horizontally past each other. P ◦ Example in the Philippines: The Marikina Valley Fault System, also known as the West Valley Fault, is a major strike- slip fault in the Philippines and is considered one of the most active fault lines in the country. O C T N E D U 1. Types of Faults: T ◦ Normal Faults: Occur when the crust is extended. The hanging wall moves downward relative to the footwall. S Common in divergent boundaries. Image from https://sites.pitt.edu/~cejones/GeoImages/7Structures/ NormalFaults.html If you stood on the fault plane, the block on the right would be under your feet. This is thus the footwall. The red line marks equivalent layers on opposite side of the fault. Since the hanging wall dropped relative to the footwall, this is clearly a normal fault. ◦ Reverse (Thrust) Faults: Occur when the crust is compressed. The hanging wall moves upward relative to the footwall. Common in convergent boundaries. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 12 of 22  San Andreas Fault At the San Andreas Fault in California, the North American Plate and the Pacific Plate slide past each other along a giant fracture in Earth's crust. Y P O C 2. Mechanics of Faulting: T ◦ Faults are fractures in the Earth's crust where blocks of land have moved relative to each other. The stress build-up along these faults eventually exceeds the strength of rocks, causing them to break and slip, leading to an earthquake. N E Tectonic Plates D Overview: U The Earth's lithosphere is divided into several large and small pieces known as tectonic plates. These plates float on the semi- T fluid asthenosphere beneath them and are constantly moving, albeit very slowly, due to convection currents in the mantle. S Plate tectonics Plate Tectonics is the theory supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. Slip on faults that define the plate boundaries commonly results in earthquakes. Several styles of faults bound the plates, including thrust faults along which plate material is subducted or consumed in the mantle, oceanic spreading ridges along which new crustal material is produced, and transform faults that accommodate horizontal slip (strike slip) between adjoining plates. See also "This Dynamic Earth: The Story of Plate Tectonics". Seismicity. Seismicity refers to the geographic and historical distribution of earthquakes. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 13 of 22 Types of Plate Boundaries: 1. Divergent Boundaries: ◦ At divergent boundaries, tectonic plates move apart from each other. This is commonly seen in mid-ocean ridges, where new oceanic crust is formed. An example is the Mid-Atlantic Ridge. 2. Convergent Boundaries: ◦ At convergent boundaries, tectonic plates move toward each other. This can result in one plate being forced beneath another in a process known as subduction. An example is the boundary between the Indian Plate and the Eurasian Plate, which has formed the Himalayas. Y Transform Boundaries: P 3. ◦ At transform boundaries, plates slide past each other horizontally. These boundaries often cause earthquakes due to the O friction and pressure built up as the plates move. An example is the San Andreas Fault in California. C 4. Plate Movements: ◦ The movement of these plates can lead to earthquakes, volcanic activity, and the creation of mountain ranges. The T interaction of plates at their boundaries is the primary driver of seismic activity. N Tectonic Plates and the Philippines E The Philippines is located at the convergence of several tectonic plates, making it one of the most seismically active regions in the world. The major tectonic plates that affect the Philippines are: D 1. Philippine Sea Plate: U ◦ This oceanic plate is moving westward and subducts beneath the Eurasian Plate along the Philippine Trench, which is T responsible for many of the earthquakes in the eastern part of the Philippines. S 2. Eurasian Plate: ◦ The western boundary of the Philippine Sea Plate, where it converges with the Eurasian Plate, forms the Manila Trench. This interaction causes earthquakes and has the potential to generate tsunamis. 3. Sunda Plate: ◦ To the south, the interaction between the Philippine Sea Plate and the Sunda Plate creates the Sulu and Celebes Sea regions, which are also seismically active. Seismic Zones of the Philippines The Philippines is divided into several seismic zones, reflecting the distribution of tectonic activity across the archipelago. These zones are areas where earthquakes are more likely to occur due to the proximity of active faults and plate boundaries. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 14 of 22  ◦ Includes the West Valley Fault System, the Manila Trench, and the Philippine Fault Zone. This area has a high concentration of active faults and has experienced significant earthquakes, such as the 1990 Luzon earthquake (magnitude 7.8), which caused widespread damage and loss of life. 2. Visayas Seismic Zone: ◦ This zone includes the Philippine Fault Zone running through Leyte and Samar, as well as the Negros Trench. An example of a significant earthquake in this region is the 2013 Bohol earthquake (magnitude 7.2), which caused extensive damage and loss of life in Bohol and Cebu. 3. Mindanao Seismic Zone: Y ◦ Includes the Cotabato Trench and the Philippine Fault Zone running through Mindanao. The 1976 Moro Gulf earthquake (magnitude 7.9), which generated a deadly tsunami, is one of the most significant seismic events in this P zone. Summary of the Relationship: O C Stress Accumulation: In all three fault types, stress builds up in the Earth's crust due to tectonic forces (tension, compression, or shearing). T Sudden Release of Energy: When the stress exceeds the strength of the rocks, a sudden movement along the fault occurs, N releasing energy in the form of seismic waves, which we perceive as an earthquake. E Earthquake Characteristics: The type of fault influences the characteristics of the earthquake, including the direction of ground movement, the depth at which it occurs, and the potential damage it can cause. D Understanding these fault movements helps explain why and how earthquakes happen, emphasizing that they are the Earth's way of U releasing accumulated stress along fault lines. T References: S Philippine Institute of Volcanology and Seismology. (2020). Earthquake Frequently Asked Questions. PHIVOLCS. https:// www.phivolcs.dost.gov.ph/index.php/earthquake/earthquake-faqs United States Geological Survey. (2021). Understanding Plate Tectonics. USGS. https://www.usgs.gov/educational-resources/ understanding-plate-tectonics Lagmay, A. M. F., et al. (2008). The Philippine fault: Active shear fault in the Philippines. Philippine Journal of Science, 137(1), 105-116. Minsan, M. C., et al. (2017). Seismic Hazards of the Philippines: An Overview. Journal of the Geological Society of the Philippines, 73(2), 87-104. Summary of the Relationship: Stress Accumulation: In all three fault types, stress builds up in the Earth's crust due to tectonic forces (tension, compression, or shearing). CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 15 of 22  Earthquake Characteristics: The type of fault influences the characteristics of the earthquake, including the direction of ground movement, the depth at which it occurs, and the potential damage it can cause. Understanding these fault movements helps explain why and how earthquakes happen, emphasizing that they are the Earth's way of releasing accumulated stress along fault lines. Y P O C T N E D U T S CHAPTER 3 MEASUREMENT OF EARTHQUAKES: MAGNITUDE VERSUS INTENSITY CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 16 of 22 Scientists measure both the energy released in an earthquake and its damage. In 1902, Italian scientist Giuseppe Mercalli introduced a scale that measures the intensity of an earthquake based on its effects on people and structures. A modified version of his scale is still in use today. The 12-point Modified Mercalli Intensity Scale describes how an earthquake is felt and the damage that it causes. The higher the Mercalli number is, the more damage found in the area. The Modified Mercalli number assigned to a particular location varies based on factors such as the distance from the focus and the area’s geology. For example, houses built on softer sediments may receive greater damage than those built on bedrock. The amount of energy an earthquake releases is expressed in terms of its magnitude. Unlike intensity, which varies depending on how populated an area is, the magnitude of an earthquake is the same no matter where you are. To measure the magnitude of an earthquake, the American scientist Charles Richter developed a scale in 1935. Known as the Richter scale, it assigns a number based on the height of the waves on a seismogram (the visual output of a seismograph). Seismographs measure ground motion, including the energy released by an earthquake. Y In 1979, American scientist Thomas Hanks and Japanese scientist Hiroo Kanamori introduced a new and more precise scale for measuring the magnitude of earthquakes: the moment magnitude scale. This is the scale most scientists use today. Its ratings are P based on physical evidence, particularly the geometry of the earthquake. To determine each earthquake’s assigned number, scientists compare the area of the rupture along a fault to the amount of energy released. Scientists prefer the moment magnitude scale over the O Richter scale because it can more accurately compare various types of earthquakes—big or small, near or far—at the same scale. Even though earthquakes with moment magnitudes of 5 or 6 can cause damage, in general, only earthquakes with a moment magnitude of 7 or higher are classified as “major” earthquakes. C Source: https://ww2.kqed.org/quest/2016/04/15/measuring-earthquakes-intensity-and-magnitude/ T Earthquakes are measured and described using two primary concepts: magnitude and intensity. These terms, while related, describe N different aspects of an earthquake and are measured in distinct ways. E 1. Magnitude D Magnitude refers to the amount of energy released at the source of the earthquake. It is a single number that quantifies the size of the earthquake. The most commonly used scale to measure magnitude is the Richter scale, though the Moment Magnitude Scale (Mw) U is more widely used today due to its accuracy in measuring large earthquakes. T Richter Scale: Developed in 1935 by Charles F. Richter, it is a logarithmic scale where each whole number increase represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release. S Moment Magnitude Scale (Mw): This scale measures the total energy released by an earthquake, taking into account the area of the fault that slipped, the amount of slip, and the strength of the rocks involved. It provides a more accurate estimate of larger earthquakes. Example: A magnitude 5.0 earthquake releases approximately 31.6 times more energy than a magnitude 4.0 earthquake. 2. Intensity Intensity, on the other hand, measures the effects of an earthquake at specific locations. It describes how strongly the ground shakes at a particular place and the resulting damage and human perception. Intensity is measured using different scales, with the Modified CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 17 of 22  Philippine Earthquake Intensity Scale (PEIS): The PEIS is a scale from I to X that categorizes the intensity of an earthquake based on observed effects on people, structures, and the environment in the Philippines. Magnitude / Intensity Comparison Magnitude and Intensity measure different characteristics of earthquakes. Magnitude measures the energy released at the source of the earthquake. Magnitude is determined from measurements on seismographs. Intensity measures the strength of shaking produced by the earthquake at a certain location. Intensity is determined from effects on people, human structures, and the natural environment. The following table gives intensities that are typically observed at locations near the epicenter of earthquakes of different magnitudes. Y Typical Maximum Magnitude Modified Mercalli Intensity P 1.0 - 3.0 I O 3.0 - 3.9 II - III 4.0 - 4.9 IV - V 5.0 - 5.9 VI - VII C 6.0 - 6.9 VII - IX 7.0 and higher VIII or higher T N Abbreviated Modified Mercalli Intensity Scale I Not felt except by a very few under especially favorable conditions. E II Felt only by a few persons at rest, especially on upper floors of buildings. D III Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated. U IV Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. T V Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. S VI Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. VII Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. VIII Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. IX Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. X Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. XI Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly. XII Damage total. Lines of sight and level are distorted. Objects thrown into the air. Source: https://earthquake.usgs.gov/learn/topics/mag_vs_int.php CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 18 of 22 Essentially, each successive magnitude is 33 times larger than the last. That means a magnitude-8.0 earthquake is 33 times stronger than a 7.0, and a magnitude-9.0 earthquake is 1,089 (33 x 33) times more powerful than a 7.0 — the energy ramps up fast. Magnitude and Energy Below is a representation, from the Geological Society of America, of earthquake magnitudes and the equivalent energy release. (For the life of us, we don't know why the geologists used pounds of explosive as a proxy for energy instead of a real physical unit of energy, such as Joules! But the figure makes the point, anyway.) Y P O C T N E D Notice the relationship is not linear? The change in the amount energy released from one magnitude to the next is greater as U the earthquake magnitude increases. For example, the difference in amount of energy released from a magnitude 5 to a magnitude 10 is not double, it is 30 million times as much! T Need some further practice relating Earthquake Magnitude to Energy? No problem, the USGS calculates the difference between a 5.8 S and 8.7 earthquake and has a calculator where you can input your own numbers to see how much bigger an earthquake can get with different magnitudes. The currently used magnitude scale for the energy released in an earthquake is officially named the moment magnitude scale, written MW. It is an exponential scale. An increase of one unit on the scale represents an increase in energy released by a factor of 32. An increase of two units represents an increase in energy release 1,000 times larger. This means that to dissipate the energy of one magnitude 7 earthquake, you would need to have 1,000 magnitude 5 earthquakes. An increase of 0.2 on the magnitude scale represents a doubling of energy released. An earthquake with MW = 6.0 releases 6.3 x 1013 joules (63 terajoules) of energy, about the energy of a small atomic bomb. The largest earthquake measured so far, the Great Chilean earthquake of 1960, had MW = 9.5. An older standard known as the Richter scale was also an exponential scale. Each increase of one unit on the Richter scale represented an order of magnitude (i.e., x10), increase in the amplitude of the motion of the ground. The moment magnitude scale has been adjusted to match the Richter scale for magnitudes under 8. For magnitudes above 8, the Richter scale becomes meaningless. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 19 of 22 The increase of energy by a factor of 1,000 for a two-unit increase in magnitude is set by the exponential nature of the moment magnitude scale. According to this definition, an increase of one unit will release 31.6 times the energy, the square root of 1,000. Since adding one unit twice is the same as multiplying by the energy increase twice, 31.62 = 1,000. Note: The equation for energy released, E, in terms of moment magnitude, MW, is: E = E0 31.6^MW or also E = E0 10^(1.5*Ms) Where E0 is an energy constant = 6.3x104 J, the energy of a magnitude 0 earthquake. Y Note 10^1.5 = 31.6 P Difference Between Magnitude and Intensity O C Magnitude is a measure of the total energy released by an earthquake and is a single value for each event, regardless of where it is felt. T Intensity describes the severity of shaking and damage experienced at specific locations, and therefore, can vary across N different areas for the same earthquake. E Example: D A magnitude 7.0 earthquake might have an intensity of IV (Moderately Strong) in a distant city, but an intensity of VIII (Very Destructive) near the epicenter. U 3. PEIS Intensity Scale T S The PEIS is used to describe the intensity of earthquakes in the Philippines. The scale is detailed below with example scenarios: Intensity I: Scarcely Perceptible. Only felt by a few individuals at rest indoors, particularly on upper floors of buildings. ◦ Example: People sitting quietly on the third floor of a building in Manila barely feel a faint shaking. Intensity II: Slightly Felt. Felt by few individuals at rest indoors. Hanging objects may swing slightly. ◦ Example: A person resting on a sofa in Davao City notices a light, brief shaking, but others around them do not. Intensity III: Weak. Felt by many people indoors, especially in upper floors of buildings. Vibrations are felt like a passing truck. ◦ Example: Residents in Cebu City on the 5th floor of an apartment building feel a mild swaying motion. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 20 of 22  ◦ Example: In Baguio City, most people inside houses feel the ground move, and some are woken up from sleep. Intensity V: Strong. Generally felt by most people indoors and outdoors. Some people are frightened; some are awakened. Hanging objects swing violently. Vehicles may rock noticeably. ◦ Example: In Quezon City, hanging lights swing and most people indoors rush outside in panic. Intensity VI: Very Strong. Many people are frightened; many run outdoors. Some people lose their balance. Motorists feel like driving on a flat tire. Heavy furniture may move. ◦ Example: In Legazpi City, people struggle to stand, and furniture shifts slightly across floors. Y P Intensity VII: Destructive. Most people are frightened and run outdoors. People find it difficult to stand in upper floors. Heavy furniture and appliances topple. Some well-built buildings are slightly damaged. ◦ O Example: In Zamboanga City, people see cracks appearing in walls and some heavy cabinets tipping over. C Intensity VIII: Very Destructive. People panic and find it difficult to stand even outdoors. Many well-built buildings are considerably damaged. People struggle to walk or stand. T ◦ Example: In Cagayan de Oro, significant structural damage occurs in multiple buildings, and the ground shakes violently. N Intensity IX: Devastating. People are forcibly thrown to the ground. Well-built buildings are heavily damaged or destroyed. E Ground fissures and landslides occur. D ◦ Example: In Tacloban, the shaking is so intense that entire buildings collapse, and the landscape changes with visible ground ruptures. U Intensity X: Completely Devastating. Practically all man-made structures are destroyed. Massive landslides and liquefaction T may occur. A significant portion of the ground is deformed. S ◦ Example: A rare and catastrophic event where a city, such as those near major fault lines, is leveled. Interactive Activity: Understanding Earthquake Intensity Objective: Students will apply their knowledge of earthquake intensity by analyzing scenarios and assigning appropriate PEIS levels. Activity: 1. Scenario Analysis: Present the students with the following scenarios and ask them to determine the PEIS intensity level. ◦ Scenario 1: A person in a high-rise building in Manila feels a gentle swaying motion but notices nothing unusual around them. CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 21 of 22  ◦ Scenario 3: A strong earthquake in Quezon City causes people to run outside in fear, and several pieces of heavy furniture tip over in homes. References: Philippine Institute of Volcanology and Seismology. (2020). Earthquake frequently asked questions. PHIVOLCS. https:// www.phivolcs.dost.gov.ph/index.php/earthquake/earthquake-faqs United States Geological Survey. (2021). The Modified Mercalli Intensity Scale. USGS. https://www.usgs.gov/natural-hazards/ earthquake-hazards/science/modified-mercalli-intensity-scale Y U.S. Geological Survey. (2021). Moment magnitude, Richter scale – what are the different magnitude scales, and why are there so many? https://www.usgs.gov/faqs/moment-magnitude-richter-scale-%E2%80%93-what-are-different-magnitude-scales-and- P why-are-there-so-many O C T N E D U T S CE 116-EARTHQUAKE ENGINEERING PANGASINAN STATE UNIVERSITY RIZALYN C. ILUMIN, MSME, MSCE URDANETA CAMPUS (1st Sem, AY 2024-2025) Instructor Page 22 of 22