Module 1 Seismology PDF

Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in...

Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering Module No.1: Seismology Contents 1.1 Seismology 1.2 Origin of Earthquakes 1.3 Causes of Earthquakes 1.4 Types of Earthquakes Reporter: Bermejo, Mark Dennis 1.1 Seismology - is the scientific study of earthquakes and the propagation of elastic waves through the Earth. - Seismology came from two ancient Greek words “seismos” and “logos”. Seismos means earthquake while logos means science. Paleoseismology -a related field that uses geology to infer information regarding past earthquakes. Engineering seismology - is the study and application of seismology for engineering purposes. It generally applied to the branch of seismology that deals with the assessment of the seismic hazard of a site or region for the purposes of earthquake engineering. - a link between earth science and civil engineering. Two Principal Components of Engineering Seismology 1. Studying earthquake history (e.g. historical and instrumental catalogs of seismicity) and tectonics to assess the earthquakes that could occur in a region and their characteristics and frequency of occurrence. 2. Studying strong ground motions generated by earthquakes to assess the expected shaking from future earthquakes with similar characteristics. These strong ground motions could either be observations from accelerometers or seismometers or those simulated by computers using various techniques!, which are then often used to develop ground motion prediction equations(or ground-motion models). Page 1 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering Earthquake Measurements Magnitude - A measure of the size of the earthquake source, which is the same number no matter where you are or what the shaking feels like. Intensity - A measure of the shaking and damage caused by the earthquake, which varies from location to location. Seismologist - The one who study about seismology. - Not only study the earthquakes as they happen, but also try to create models to predict when and where might occur. They also the effects of earthquakes, like seismic waves and tsunamis. FAMOUS SEISMOLOGISTS Charles Francis Richter (1900-1985)  Developed Richter Scale, to measure the magnitude of earthquakes.  He believe that the " The magnitude value was proportional to the logarithm of amplitude of the strong wave during an earthquake" (Matter Project, 1999.  Developed Richter Scale in 1953, a device used to measure the magnitude of earthquakes.  The Richter Scale has been in use for many years and is an example of a logarithmic scale. Logarithmic scales are linear scales in 'x' such as 1.0, 2.0, 3.0 etc, but they represent magnitude changes of 10, 100 and 1000. Inge Lehmann (1888-1993)  Who made a ground breaking discovery of the structure of the earth's core.  She analyzed how energy release from earthquake travel through the earth.  A Danish seismologist who made a ground breaking discovery of the structure of the earth's core in 1936. Page 2 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering Reporter: Abayog, Lenard 1.2 ORIGIN OF EARTHQUAKES Theory of Plate Tectonics - Plate tectonics is the theory that earth's outer shell is divided into several plates that glide over the mantle. - This theory is a unifying principle in geology that explains how the Earth’s surface is composed of large tectonic plates that move in relation to one another. - There are nine major plates, according to world atlas. These plates are named after the landforms found over them. The nine major plates are North American, Pacific, Eurasian, African, Indo-Austrelian, Australian, Indian, South American and Antarctic. - Most of it located under the ocean and it is moving northwest at a speed of around 7cm/year. - The largest plate is the pacific plate having area about 103,000,000 square km. - There are also many smaller plates throughout the world. How does plate tectonics work? Convection in the mantle is considered the primary driving force behind plate tectonics. The hot material near the Earth’s core rises, while the cooler mantle rock sinks, much like a pot of boiling liquid on a stove. This convection process propels the movement of tectonic plates through a combination of pushing and spreading at mid- ocean ridges and pulling and sinking at subduction zones. - Page 3 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering EARTHQUAKE - any sudden shaking of the ground caused by the passage of seismic waves through Earth's rocks. An earthquake is a natural phenomenon caused by the sudden release of energy in the Earth's crust, which creates seismic waves. 1. Focus (Hypocenter): This is the point inside the Earth where the earthquake originates. It's the location where the fault starts to slip. It is the point on the fault where rapture occurs and the location from which the seismic waves are released 2. Epicenter: The point on the Earth’s surface that is directly above the focus, the point where the earthquake originated. This is often where the effects of the earthquake are most strongly felt. 3. Fault: A fracture or zone of fractures between two blocks of rock. The movement along the fault causes the earthquake. Common types of faults include normal, reverse (thrust), and strike- slip. 4. Seismic Waves: These are waves of energy that travel through the Earth. They include: - Primary Waves (P-waves): These are compressional waves that travel fastest and arrive first. They move through solids, liquids, and gases. - Secondary Waves (S-waves): These are shear waves that move slower than P-waves and arrive second. They move only through solids. Page 4 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering - Surface Waves: These travel along the Earth's surface and usually cause the most damage. They include Love waves (which move horizontally) and Rayleigh waves (which create a rolling motion) 5. Aftershocks: These are smaller earthquakes that occur in the same region after the initial earthquake as the Earth's crust adjusts. 6. Foreshocks:These are smaller tremors that can precede the main earthquake. They may occur days or even years before the main event. 7. Seismograph: An instrument used to detect and record the seismic waves produced by earthquakes. It helps in determining the magnitude and location of the quake. Understanding these components helps in studying earthquakes and mitigating their impact. Reporter: Bolo, Marlo SEISMIC WAVES: - Seismic wave is a mechanical wave of acoustic energy that travels through the Earth caused by earthquake. - Earthquakes are caused by the sudden release of energy, producing waves that causes the movement of the earth. Those waves are called Seismic waves. There are two types of Seismic waves the body waves and the surface waves. The body waves travels internally through the body of the earth that is why it is called body waves. The surface waves spreads across the surface of the earth. Body waves [Primary(P) waves, Secondary(S) waves] Primary(P) waves Secondary(S) waves Page 5 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering 2 types of waves under body waves  P-waves A.K.A. Primary waves - faster than the S-waves and causes the earth to move forward and backward or it compresses and expands the earth.  S-waves A.K.A secondary/shear waves - causes the earth to moves up and down or in a shearing movement. Surface waves [Love wave, Rayleigh Wave] Love wave Rayleigh Wave 2 types of waves under surface waves  Love waves - causes the earth to move side to side perpendicular to the direction of the wave  Rayleigh waves - causes the earth to move in a rolling circular motion. Reporter: Simara, Danilo III 1.3 Causes of Earthquakes Earthquakes are natural phenomena that occur when the Earth's surface experiences sudden and intense shaking due to the release of energy stored in its crust. These tremors can have devastating impacts, from minor vibrations to significant destruction. The causes of earthquakes can be categorized into natural and human-made factors. These are the major causes of earthquakes. VOLCANIC ACTIVITY When boiling lava tries to break through the surface of the earth, with the increased pressure of gases, certain movements are caused in the earth’s crust. Page 6 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering - When magma rises to the Earth's surface, it creates pressure that can lead to volcanic eruptions, causing the surrounding ground to shake. These volcanic tremors are often localized around the volcano. Tectonic Movement The surface of the earth consists of some plates, consisting of the upper mantle. These plates are always moving, thus affecting the earth’s crust. - The Earth's crust is made of large plates that constantly move. When these plates collide, pull apart, or slide past each other, the accumulated stress is released as seismic energy, resulting in an earthquake. Geological Faults A geological fault is known as the displacement of plates of their original plane. The movement of rocks along these planes brings about tectonic earthquakes. - Fault lines are fractures in the Earth's crust where sections of rock have moved. When stress builds up along these faults, it can lead to sudden movements that cause earthquakes. Man-Made The interference of man with nature can also become a cause of the earthquakeNuclear bombing can send specific types of shockwaves throughout the surface of the earth, which can disturb the natural alignment of tectonic plates. - Man-Made Causes: Human activities such as mining, drilling, or constructing large reservoirs can induce seismic activity by altering the Earth's natural stress balance, leading to minor or significant earthquakes. Page 7 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering Minor Causes Some minor causes such as landslides, avalanches, the collapse of heavy rocks, etc. can also cause minor shockwaves. The gases beneath the surface of earth contract and expand, giving rise to movements in plates beneath the crust. - Natural events like avalanches, landslides, and even large-scale rockfalls can cause the ground to shake, but these tremors are generally less severe and more localized. Reporter: Regaspi, Samuel and Vargas, Neil Christian 1.4 Types of Earthquakes Causes of Earthquakes from which these are the underlying reasons why earthquakes occur. While these types of earthquakes refer to the different ways earthquakes can manifest based on their causes or characteristics., specifically the 4 types of earthquakes: tectonic, volcanic, explosion and collapse. These natural phenomena can have devastating consequences, but understanding their causes and characteristics can help us better prepare and respond to them. Classification based on the Cause of Origin A. Tectonic Earthquake - Earthquakes caused by tectonic plates are called tectonic quakes. These are the most occurred earthquakes worldwide and usually occur at the boundaries of the tectonic plates - These are caused by the sudden release of energy stored in rocks deformed by tectonic forces. Earthquakes caused by tectonic plates are called tectonic quakes. These are the most occurred earthquakes worldwide and usually occur at the boundaries of the tectonic plates. Page 8 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering Examples of Tectonic Earthquake San Francisco earthquake of 1906. The devastating quake, caused by the San Andreas Fault, destroyed much of the city. Tohoku earthquake of 2011 in Japan. This powerful quake triggered a devastating tsunami, highlighting the interconnectedness of these natural disasters. And the very latest earthquake was happened in the offshore eastern Mindanao of the southern Philippines on August 3, 2024 resulted from renewed movement of an extinct fracture zone subducting into Earth’s mantle. Page 9 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering B. Non-Tectonic Earthquake The non-tectonic earthquakes are the ones associated with other causes. Volcanic Earthquakes - caused by the movement of magma beneath the Earth’s surface. Occur in conjunction with volcanic activity, usually preceding or following a volcanic eruption. - These earthquakes are associated with volcanic activity, often indicating that magma is on the move beneath the surface. Caused by the movement of magma beneath the Earth’s surface. Occur in conjunction with volcanic activity, usually preceding or following a volcanic eruption. Example of Volcanic Earthquake: The 1991 eruption of Mount Pinatubo in the Philippines was preceded by a series of volcanic earthquakes. These quakes served as a warning sign, allowing for evacuations and preparations. The Department of Science and Technology-Philippine Institute of Volcanology an Seismology (DOST-PHIVOLCS) reported a sudden phreatic eruption at Mayon Volcano at 6:16 p.m. on July 18, 2024. Explosion Earthquakes - These earthquakes result from the explosion of chemical and nuclear devices. It can be measured by the motion of large tectonic earthquakes using a GPS device because the rocks on either side of the fault are offset during this type of earthquake - These are triggered by human activities, such as mining, reservoir-induced seismicity (due to large dams), or hydraulic fracturing commonly known as fracking, is a technique used to extract oil and natural gas from deep underground rock formations thru drilling and extraction. Page 10 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering - Whereas explosion earthquakes are immediate and result from a sudden, intense release of energy. - Induced earthquakes and explosion earthquakes are not the same, though they can both be caused by human activities. Example of Explosion Earthquake: The atomic bombings of Hiroshima and Nagasaki, marking the end of World War II, demonstrate the devastating power of nuclear weapons. These were the only instances of atomic bombs used in conflict, causing unimaginable destruction. The tests of nuclear bombs. For instance, the underground nuclear tests conducted by various countries, such as the tests at the Nevada Test Site in the United States, caused small earthquakes. The powerful explosions generated seismic waves similar to natural earthquakes. Collapse Earthquakes - Collapse earthquakes are compelled by the pressure produced within the rocks. This kind of earthquake leads to the collapse of the roof of the mines compelling more tremors. - Occur when a cave or underground mine collapses, causing the ground above to shake. Example of Collapse Earthquake: One example of a collapse earthquake occurred in the Sichuan region of China in 2008. Page 11 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering This 7.9 magnitude earthquake was caused by the collapse of mountains around the Wenchuan region. The earthquake left more than 69,000 people dead or missing and damaged thousands of buildings and infrastructure. It also caused landslides and flooding that threatened the safety of local communities. Classification based on Depth of Focus Surface Earthquake - Surface earthquake are those in which the depth of the focus is less than 10km. Example of Surface Earthquake 2011 Christchurch Earthquake, New Zealand One notable example of a surface earthquake is the 2011 Christchurch Earthquake, which struck near Christchurch, New Zealand, on February 22, 2011. This earthquake had a magnitude of 6.3 and occurred at a shallow focus depth of approximately 5 kilometers. The proximity of the epicenter to the city and the shallow depth resulted in intense shaking and significant damage to buildings and infrastructure. Shallow Earthquake - The earthquake with the hypocenter at a depth of 10 to 50 km. Example of Surface Earthquake 2010 Haiti Earthquake Page 12 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering The 2010 Haiti Earthquake occurred on January 12, 2010, with a magnitude of 7.0. The hypocenter was located at a depth of about 13 kilometers, making it particularly destructive due to its shallow nature. The earthquake struck near Port-au-Prince, Haiti's capital, resulting in catastrophic damage across the region. The combination of the earthquake's magnitude, shallow depth, and the densely populated urban environment led to an estimated 230,000 fatalities and left millions of people homeless, underscoring the devastating impact of shallow seismic events. Deep focus earthquake - The deep focus earthquake or plutonic earthquake are those with hypocenter located at depth more than 300 km. - Majority of deep focus earthquake are originated between 500 to 700 km. Example of Deep Focus Earthquake This map shows May 24, 2013 earthquake and historical seismicity with epicenter depths and magnitudes An example of a deep focus earthquake is the 2013 Okhotsk Sea Earthquake, which occurred on May 24, 2013. This earthquake registered a magnitude of 8.3 and had a remarkable hypocenter depth of approximately 609 kilometers, making it one of the deepest earthquakes recorded. Located off the coast of the Kamchatka Peninsula in Russia, the deep focus of this earthquake meant that it caused relatively little surface damage compared to shallower events. While it was felt in nearby regions, the depth significantly mitigated its impact, demonstrating how deep focus earthquakes can release substantial energy without causing widespread destruction. Page 13 of 14  Republic of the Philippines CAMARINES SUR POLYTECHNIC COLLEGES Nabua, Camarines Sur COLLEGE OF ENGINEERING AND ARCHITECTURE Bachelor of Science in Civil Engineering REFERENCE: Seismology Definition, History & Earthquakes. (n.d.). https://study.com/academy/lesson/seismology-definition-history.html Michigan Technological University. (2021b, October 4). Seismology. https://www.mtu.edu/geo/community/seismology/learn/seismology-study/ British Geological Survey. (2021, June 10). What causes earthquakes? - British Geological Survey. https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/what- causes-earthquakes/ What is an earthquake and what causes them to happen? | U.S. Geological Survey. (2021, December 31). https://www.usgs.gov/faqs/what-earthquake-and-what-causes-them- happen Michigan Technological University. (2021, August 11). Why Do Earthquakes Happen? https://www.mtu.edu/geo/community/seismology/learn/earthquake-cause/ Earthquake Types: What You Need to Know. (2022, March 27). Unacademy. https://unacademy.com/content/nda/study-material/geography/earthquake-types/ What Happens During an Earthquake? (n.d.). Caltech Science Exchange. https://scienceexchange.caltech.edu/topics/earthquakes/what-causes-earthquakes Seismology https://www.slideshare.net/slideshow/seismology-123961467/123961467 SE - 412 EARTHQUAKE ENGINEERING GROUP 1 MEMBERS: (Reporters/Discussants) Abayog, Lenard Bermejo, Mark Dennis Bolo, Marlo Regaspi, Samuel Simara, Danilo III Vargas, Neil Christian (PowerPoint Presentation) Jacob, Kent Justin (Content/Data) Balana, Mark Edlian Llagas, Angelika Ortega, Loriemie Pontillas, Rica Joy Page 14 of 14