News from the Field: Day 7--Geophysical Experiment

A new guest joined us today: Ken Austin from the University of Southern California. Ken is a graduate student in geophysics who is studying active deformation of California using Global Positioning System (GPS) measurements. We spent part of the morning at SNARL, reviewing USC's current research on active deformation in and around Long Valley. Ken then trained the group on setup and operation of state-of-the-art geophysical monitoring equipment--GPS receivers, a high-precision gravity meter, and a magnetometer. We learned how to set up, operate, and analyze data from these geophysical instruments. The group then headed out to McGee Creek to do some measurements on one of the region's most active faults--the Hilton Creek Fault. We examined a remarkable exposure of the fault, where it crosses--and offsets--a recent glacial moraine. Ken joined us for another great dinner back at SNARL, followed by a lively game of 'Maui' around the dinner table.

May 29th

*Ken Austin from USC starts off the day with an introductory presentation on GPS measurements of crustal deformation at Long Valley*
*Once the clouds break, we get a beautiful view of the McGee Creek valley, and the high Sierra.*
*And a beautiful view down McGee Creek towards the Owens Valley*
*Ken demonstrates how to set up a surveying tripod and GPS equipment, while Josh and Matt look on.*
*Michael tries out the optical plummet, while Josh looks on.*
*Now Mia tries her hand, while Emily looks on.*
*Ruben adjusts the tribrach, while Mia looks on...*
*Now the students try it on their own: Ryan, Michael, Sam, and Emily team up.*
*Kat centers the tripod over the mark...*
*Ryan slips the antenna on, and Michael makes sure he's doing it right.*
*Liz and Ruben carefully measure the height of the antenna.*
*Ruben, Liz, Josh, and Ken check on the GPS receiver*
*Are we having fun yet?*
*John and Matt work on their tripod, in the blowing wind...*
*The sun comes out for a moment, and the geophysicists work on evening their tans...*
*And Brandy finds a cozy place to hide from the wind...*
*Ken introduces the group to another geophysical instrument--a gravity meter.*
*While Michael talks to the group about gravity theory...*
*Then Michael gets Matt and Debby set up with a magnetometer--to measure variations in the Earth's magnetic field.*
*And off they go!*
*Josh and Ruben try their hand at the magnetometer...*
*A hike up the moraine affords a great view of the Hilton Creek Fault. (Hint: follow the green vegetation across the valley to the moraine on the opposite flank)*
*Michael and Kat work on their sketches of the fault from a great perspective at the top of the moraine.*
On our way down, the group discovers a remarkable glacial boulder containing a faulted xenolith, which has been intruded by a younger magmatic intrusion. We discover five generations of magmatism and tectonics in a single rock!
*Back at the ranch, the group enjoys a view of yesterday's website.*