Geology 437: Seismology and Magnetics; Optional (& free!) Take Home Exam

The comprehensive final exam is worth about 35% of your course grade, the midterm 30%.   If you do this optional take home final, I will count it as 50% of the final exam grade or midterm exam grade (whichever helps most).

Rule: You can talk over how to do surveys and problems, but I want everybody to do their own work and writing - federal rules preclude collusion and price fixing. Due on or before Friday, December, 16th, 12:01 pm.:

Part One - Request For Bid: Possible mineralized dike beneath glacial till

A group of investors is interested in testing, by drilling, the mineralization and economic potential of a mineralized basaltic dike they suspect is buried beneath glacial debris. To minimize drilling costs, they want a combined ground magnetic and seismic refraction investigation.

Knowns:

• The site is 50 km from Missoula, and nearby dikes strike about 90 degrees (due east)
• The glacial debris, dry at the surface, is somewhere between 5m and 20 meters thick and transmits P-waves at 1,200 m/s
• The magnetic susceptibility of the dike is 0.12 in the SI system
• The dike (Vp=2,100 m/s) crosscuts gneisses of the same velocity and is 10 meters thick

Factors to be determined:

• location of the dike
• confirm the strike and determine the dip of the dike
• thickness of glacial overburden above the dike
• general topography of the bedrock surface
• whether groundwater will be a problem if mining proceeds

The bidding contractor is responsible for experimental design, fieldwork, data acquisition, data processing, and interpretation.  You should specify the equipment from my lab that you will use but need not include rental expense in your bid (that'll be a congressional scale kickback).

Your submitted bid should include:

• brief introduction with a concise description of the problem and the equipment to be used
• description of your proposed magnetic and seismic surveys based on preliminary models (Magcad & spreadsheet refraction)
• description/explanation of your proposed procedures (so they can be evaluated and compared to other bids)
• summary of possible problems/limitations of the surveys
• statement of why your proposed experiments will be successful
• description of the project report you intend to submit on completion  (nature of data, figures and graphs)
  
• detailed breakdown of your survey costs and your total bid for the refraction component of the project.  You should consider travel time, time in the field, time in the lab, and time to write the report; base it on $40/hour.

Constraints:

• Assume the location is known within a square kilometer
• The clients only want two refraction lines of length 250 meters but they can be made of several shorter segments if that is optimal.

Your bid should be no longer than four printed pages not including figures or maps.  If you need to you may include additional items in an appendix.

Part Two - Locate the Epicenter

Given the station locations and differences in P-wave and S-wave travel times below, use the T-delta chart, Excel, spherical trig, and a least squares constraint to find the best fit epicenter (latitude, longitude). Print the T-delta chart at a full page size and carefully measure the time differences.

• Include a careful explanation of your procedures and an operational spreadsheet.
• Include a plot showing station locations and your epicenter determination
• What happens to the accuracy of your solution if you do not use the observation from Tokyo? Why?