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- G 209
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Course DescriptionCovers the nature and origin of earthquakes, the characteristics of seismic waves, how earthquakes are measured, the hazards of earthquakes and the historical and geological record of earthquakes. Prerequisites: WR 115, RD 115 and MTH 65 or equivalent placement test scores. Audit available.
Addendum to Course Description
Earthquakes (G209) is a one-term introductory course in earthquakes/seismology, which is a branch of the science of geology. The student will develop an understanding of the causes, activity, effects, and hazards of earthquakes as well as an understanding of the various methods of measuring the size/energy of an earthquake. The course will use case studies of historical earthquakes to examine ways to minimize earthquake damage, with emphasis on earthquakes in the pacific northwest. This course can be used to partly fulfill graduation requirements for the Associate Degree, and has been approved for block transfer. The text and materials have been chosen by the faculty and the emphasis of the course will be the viewpoint of the author(s). This includes the geologic time scale and the evolution of the Earth.
Regarding the teaching of basic geologic principles (such as geologic time and the theory of evolution), the Portland Community College Geology Department stands by the following statements about what is science.
- Science is a fundamentally non-dogmatic and self-correcting investigatory process. A scientific theory is neither a guess, dogma, nor myth. The theories developed through scientific investigation are not decided in advance, but can be and often are modified and revised through observation and experimentation.
- Creation science, also known as scientific creationism, is not considered a legitimate science, but a form of religious advocacy. This position is established by legal precedence (Webster v. New Lenox School District #122, 917 F.2d 1004).
- Geology instructors at Portland Community College will teach the generally accepted basic geologic principles (such as geologic time and the theory of evolution) not as absolute truth, but as the most widely accepted explanation for our observations of the world around us. Instructors will not teach that creation science is anything other than pseudoscience.
- Because "creation science", "scientific creationism", and "intelligent design" are essentially religious doctrines that are at odds with open scientific inquiry, the Geology/General Sciences SAC at Portland Community College stands with such organizations such as the National Association of Geoscience Teachers, the American Geophysical Union, the Geological Society of America, and the American Geological Institute in excluding these doctrines from our science curriculum.
Students are expected to be able to read and comprehend college-level science texts and perform basic mathematical operations in order to successfully complete this course.
Intended Outcomes for the course
A student who successfully completes this course should be able to:
- Use an understanding of rock mechanics, paleoseismology, and the elastic rebound theory to infer the probability that an area will be seismically active.
- Analyze the development, scope, and limitations of plate tectonics and utilize plate tectonics to explain the Earths earthquake activity.
- Access information related to seismology from a variety of sources, evaluate the quality of this information, and compare this information with current models of seismic processes identifying areas of congruence and discrepancy.
- Make field and laboratory based observations and measurements of earthquakes and landforms associated with earthquakes, use scientific reasoning to interpret these observations and measurements, and compare the results with current models of seismic processes identifying areas of congruence and discrepancy.
- Use scientifically valid modes of inquiry, individually and collaboratively, to critically evaluate the hazards and risks posed by earthquakes both to themselves and society as a whole, evaluate the efficacy of possible ethically robust responses to these risks, and effectively communicate the results of this analysis to their peers.
- Assess the contributions of seismology to our evolving understanding of global change and sustainability while placing the development of seismology in its historical and cultural context.
Course Activities and Design
The material in this course will be presented in a lecture/discussion format Other educationally sound methods may be employed such as guest lectures, field trips, research papers, and small group work.
Outcome Assessment Strategies
At the beginning of the course, the instructor will detail the methods used to evaluate student progress and the criteria for assigning a course grade. The methods may include one or more of the following tools: examinations, quizzes, homework assignments, research papers, small group problem solving of questions arising from application of course concepts and concerns to actual experience, oral presentations, or maintenance of a personal work journal.
Course Content (Themes, Concepts, Issues and Skills)
- Describe what is meant by "earthquake".
- Define the following terms: focus, epicenter, refraction, reflection.
- Describe the different types of seismic waves.
- Describe the relationship of earthquakes to plate tectonics.
- Define the following terms: strain accumulation, creep, foreshock, main shock, aftershock, interplate earthquake, intraplate earthquake.
- Describe how a seismograph works.
- Locate an earthquake epicenter using travel-time curves and three seismic records.
- Describe how earthquakes can be used to study the interior of the earth.
- Locate underground faults and describe crustal structure using a seismic profile.
- Classify the different types of faults that result from earthquakes.
- Define the following terms: strike-slip, dip-slip, oblique-slip, hanging wall, foot wall.
- Describe the landforms produced along faults.
- Describe the causes of earthquakes.
- Define the following terms: compression, dilation, elastic rebound, compressive stress, tensile stress, fault-plane diagram
- Identify the different types of seismic waves on a seismogram and determine the motion along the fault from the first motion of the p-wave.
- Describe the relationship between earthquakes, volcanoes and tsunamis.
- Define the following terms: soil liquefaction, slickensides, sand boils, clastic sills.
- Discuss a number of historical earthquakes and determine the major cause of destruction for each case.
- Describe the events that precede earthquakes.
- Describe the evidence for past earthquakes along the Cascadia subduction zone.
- Describe steps that an individual can take to protect against earthquake damage
- Describe methods for making buildings and other structures more earthquake resistant.
Topics to be covered include:
- Global Earthquake Activity
- Major historic earthquakes and their impact on society (e.g. San Francisco 1906, Mexico City 1985, Nisqually 2001 etc.)
- Number and geographic distribution of major historic earthquakes
- Observational Seismology
- Eyewitness observations during earthquakes
- Effects of earthquakes; ground rupture, ground displacement, fault scarps, sand boils, liquefaction, damage to buildings and structures
- Mercalli intensity scale
- Foreshocks and aftershocks
- Faults and Earthquakes
- Relationship between faults and earthquakes, elastic rebound theory of earthquakes
- Stress (compressive, tensional, shear) and strain (brittle, ductile and elastic)
- Types of faults: strike slip, dip slip, oblique slip, right lateral, left lateral, normal, reverse, thrust and detachment, footwall vs. hanging wall, relation between fault type and stress
- Small scale features of faults; slickensides, fault gauge, mineralization.
- Geomorphology of faults; scarps, shutter ridges, sag ponds, linear valleys, faceted spurs
- Evidence for cumulative displacement along faults
- Causes of earthquakes not associated with faults; landslides, volcanic eruptions, atomic tests
- Instrumental Seismology
- Seismometers; principles of operation, sensitivity
- Seismograms; identification of P, S and surface waves
- Properties of waves; wavelength, amplitude, period, wave speed, particle motion
- Behavior of waves; constructive and destructive interference, standing waves, refraction, reflection
- Interpretation of P, S and surface waves, typical velocities of each
- Use of P-S wave gap to determine distance to earthquake, pinpointing the point of origin of an earthquake by triangulation, epicenter vs. focus
- Use of first motion studies to determine the sense of motion along a fault, use of 'beach ball diagrams' to represent fault plane solutions
- Determining the magnitude of an earthquake; Richter magnitude vs. moment magnitude
- Frequency of various size earthquakes, depth distribution of earthquakes
- Mechanics of Faults
- Creep and asperities, stick -slip models of faults
- Earthquakes triggered by earthquakes; changes in stress and strain caused by earthquakes
- Earthquakes and the Earth's Internal Structure
- Refraction and reflection of seismic waves, application to determining subsurface structure and thickness of crust
- Velocity of seismic waves through different materials, effects of pressure and temperature on seismic velocity
- Variation of seismic velocity with depth; evidence for the low velocity zone
- Shadow zones as evidence for the outer and inner core.
- Plate Tectonics and Earthquakes
- Basic idea of plate tectonics, evidence for plate motion, difference between continental and oceanic crust, internal structure of the earth, heat loss and plate tectonics
- Types of plate boundaries: stresses associated with each, first motions of earthquakes observed at each, depths of earthquakes associated with each type of plate boundary
- Living with Earthquakes
- Primary hazard from earthquakes; ground shaking, ground deformation, liquefaction
- Secondary hazards from earthquakes; landslides, tsunamis, fire
- Construction of earthquake hazard maps
- The methods of paleoseismology, the reoccurrence intervals of faults
- Preparing for earthquakes, personal preparedness, societal preparedness
- The design of earthquake resistant buildings, the retrofitting of existing buildings
- Predicting earthquakes, possible precursors, periodicity, seismic gaps
- Successes and failures of earthquake prediction in China and Parkfield, CA.
- Earthquakes in the Pacific Northwest
- Historic earthquakes in the Pacific Northwest
- Tectonic setting of the Pacific Northwest and the possibility of large earthquakes
- Evidence for prehistoric subduction zone earthquakes in the Pacific Northwest
- Comparison of causes, effects and frequency of shallow, deep and subduction zone earthquakes
- "Silent' earthquakes in the Pacific Northwest