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to GEOSC497B
Geophysics of Basin & Range Province
Course Material Print(pdf format)| Schedule "Secured" | Grading Policy | Experiments | Field Trips |
Questions to Consider when Analyzing the Data
Geophysical Techniques Reading Material
Syllabus
Meeting Time : 2:30 - 3:20 PM, MWF
Where : 6 Deike
Grading Policy
First and foremost in this course, I want everyone to have fun learning new things about geology and geophysics and working in a spectacular field area. Informality will be the usual operating principle although simple courtesy will be appreciated by all. (We will be living together for a solid week in occasional close confines.)Course grade will be based on classroom presentations, classroom participation and quality of contribution to the final field reports.
Classroom presentations include prepared presentation of selected geologic and geophysical papers from the literature, presentations concerning the operation of equipment and presentation of geophysical results at the end of the course. For the first half of the course you will be required to read assigned papers, prepare type-written abstracts of particular papers, distribute these to the class, present the paper to the class outlining all important assumptions and results, and lead the ensuing discussion. We will also be spending more time this year getting prepared for the field by working in the lab and carefully checking equipment.
Participation includes participation in discussions after oral presentations by students and faculty and helpfulness in the field.
Field reports will be group efforts with clear statements within that indicate individual contributions.
Experiments
We will be using several geophysical techniques to investigate the subsurface.
These include seismic refraction, gravity, and magnetics. In addition, we will
be using the TOPCON EDM Theodolite to accurately survey in station
locations and elevations. Last year we also attempted to install a passive
broadband seismic station on Eagle Mountain to investigate local
earthquakes. Pending the availability of seismic instruments in the
IRIS/PASSCAL instrument pool, we will try it again. (Last year's effort was
almost successful!)
Each of these of these items of equipment will be thoroughly checked and calibrated by working groups prior to work in the field. Each one of you will have the chance to operate and collect data from each instrument. Data collection will truly be a joint effort by everyone in the class.
Last year's experiment concentrated on finding a geophysical signature of a suspected lithological contrast across the Furnace Creek Fault Zone north of Shoshone, California. As a class, we will look at the local geology of the area and choose a suitable geophysical/geological target to go after.
Field Trips
Depending on the weather (which is almost always good) and problems that
we encounter in the field, we will be taking several geological field excursions
in Death Valley and the surrounding area to investigate spectacular fault
structures, desert geomorphology, and stratigraphy. We will make one or
more trips into the National Park as a group with one of the resident
geologists as well as going on several short hikes.
Living Arrangements
As in previous years, we will probably be staying at the Shoshone Education and Research Center (SHEAR) administered by Terry Pavlis at the University of Louisiana. This is a simple indoor facility that has all the amenities of home. Students will pay for room, board and vehicle fuel while in Shoshone. Last year this amounted to $144 for the entire trip. The department picked up the costs for transportation to and from California in past years and I expect the same thing to happen this year.
Questions to Consider when Analyzing the Data
General:
What structures are we trying to image in our field area?Are there other ways to collect the data to ensure a higher quality result?
What were goals of the scientific experiment as you saw them before starting?
Did these goals change? If so, why?
Surveying:
What is the accuracy of the final station locations?What are the major sources of error?
What are the locations on the map?
How were the data reduced?
Gravity:
How does the gravity meter work?How do you read it?
What is the result of comparing the data from the incorrect reading procedure and the correct reading procedure? Was it systematic or random? What were the errors.
What contributes most error to the reduced Bouguer gravity?
What are plausible geological models which explain the data?
How do you connect the gravity of this profile to the results of past profiles in the area?
Is a topographic correction needed?
Magnetics:
How does the magnetometer work?How do you read it?
Was a magnetic storm occurring on the days magnetic data were being taken? How do you find out?
Were there significant anomalies?
What are plausible geological models which explain the data?
How do the models compare to past results.
Active Seismic:
What are layer velocities along the profile?What kinds of materials do these velocities imply?
Were reflectors imaged?
What waves are contained in the raw data?
What processing techniques were used to reduce the data?
What is the profile geometry?
What is the depth of structure imaged by the experiment?
What does refraction analysis tell you?
What does reflection analysis tell you?
How can the experiment be repeated to yield better data?
What are plausible geological models which explain the data?
Passive Seismic:
What kind of events were recorded by the broadband station? (local earthquakes, local industrial blasts, teleseismic earthquakes)How many events were recorded?
What are the magnitudes of recorded events?
Is there local seismicity on nearby active faults?
Where are their locations? Can these events be correlated with data collected by the Great Basin Network or Caltech's SCARLET network?
Are there data available from the experiment to determined gross crustal and mantle structure using: receiver functions? surface wave dispersion? other observed phases?
Geophsical Techniques Reading Material(Under Construction)
Surveying
Compton, Robert S., Geology in the Field, John Wiley and Sons (1985) Look at Chapter 8 to get an overview of surveying. Skim sections on use of plane table and alidade equipment. Read section 8-7.Gravity
Dobrin and Savit, Introduction to Geophysical Prospecting, 4th ed., 1988. Chapter 12 - Skim theory, read sections about gravimeters Chapter 13 - Read sections on gravity measurements on land, reduction of gravity measurements, typical gravity anomalies for various geological features Chapter 14 - Section 14.5 on quantitative interpretationMagnetics
Chapter 15 Chapter 16, Magnetic surveys on land Skim Chapter 17Seismic Reflection
An in-depth understanding of seismic techniques requires a good mathematical background and familiarity with differential equations (the wave equation) and Fourier transforms. Don't be too concerned with understanding these aspects of theory but concentrate on the simple models of wave propagation and configuration of the experiment. Chapter 4, 7, 8 Text book by John Scales, Theory of seismic imaging. First 2 chapters.Seismic Refraction
Chapter 11
If you have any comments, send me an email to "Seung Yoo".