HR: 14:10h
AN: U23C-03 INVITED     [Abstracts]
TI: Extracting Information on Tephra Fallout Deposits With Ground Penetrating Radar
AU: * Kruse, S
EM: skruse@cas.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AU: Connor, C
EM: cconnor@cas.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AU: Martin, K
EM: ktmartin@mail.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AU: Mora, R
EM: raulvolcanes@yahoo.com.mx
AF: Escuela Centroamericana de Geología, Universidad de Costa Rica y Red Sismológica Nacional, San José, 00000 Costa Rica
AU: Ramirez, C
EM: carlosjru@hotmail.com
AF: Escuela Centroamericana de Geología, Universidad de Costa Rica y Red Sismológica Nacional, San José, 00000 Costa Rica
AU: Alvarado, G
EM: galvaradoi@ice.go.cr
AF: Escuela Centroamericana de Geología, Universidad de Costa Rica y Red Sismológica Nacional, San José, 00000 Costa Rica
AB: Numerical simulation and inversion of high resolution data on tephra fallout deposits offers an opportunity to fundamentally improve our ability to estimate eruption parameters from deposits. Traditional trenching data is insufficient to adequately constrain eruption parameters. Ground penetrating radar can change this by providing high resolution data along continuous transects, particularly where deposit thickness is too great to trench. Differences between observations and numerical simulations provide details about the physics of volcanic eruptions not captured by current models and provide clues about the limits of current models. Studies on Cerro Negro, Nicaragua and Irazú, Costa Rica demonstrate that GPR is beautifully suited to imaging tephra blankets in both dry and wet environments. Surveys with 100 and 200 MHz antennas show clear reflectors within the tephra fallout sequence are imaged to 20 meters depth. In accord with trench data, we interpret the bright reflectors as weathered horizons (paleosols in some cases) and abrupt changes in grain size that mark intervals between eruptive events. Simulations of radar wave propagation through volcanic deposits are used to examine the conditions under which useful information on weathered horizons and on ballistic dimensions can be extracted.
DE: 0689 Wave propagation (2487, 3285, 4275, 4455, 6934)
DE: 8404 Volcanoclastic deposits
DE: 8494 Instruments and techniques
SC: Union [U]
MN: Fall Meeting 2005