12.221 Field Geophysics Instructors Tom Herring, tah@mit.edu; Brad Hager brad@chandler.mit.edu Web: http://www-gpsg.mit.edu/~tah/12.221 01/20/05 12.221 IAP Class 5

Activities Today Paper outline with contributions of each student. Clean up data processing algorithms. Final results will be available after Saturday Jan 22 when the MIT final orbits for the week of Jan 9-15 become available. Tomorrow we will run gravimeter warm-up test. 01/20/05 12.221 IAP Class 5

Algorithm clean-up Main idea: Gravimeter measurements are relative and the instrument drifts with time: Processing need to know the gravity at the base station and each day and offset (and possible drift) are computed between the gravimeter measurements and this base value. The measurements are effected by earth tides and these need to accounted for. Unix program etgtab will be used. (Earth tide gravity as function of time). 01/20/05 12.221 IAP Class 5

Aspects of Paper Each student should select a part of the project that they will present. Suggestions: Regional gravity context Analysis of the “density” measurements made (Edge of wash measurements) Basic calibration of data. Drift corrections, connection to regional gravity measurements. Interpretation of gravity anomalies Terrain corrections. Impact on interpretation. 01/20/05 12.221 IAP Class 5