HR: 0800h
AN: H51E-0793    [Abstracts]
TI: Spatial and Continuous Observations of Stream Hydrodynamics and Bedload Transport From Spectral Analysis of River Induced Seismic Noise
AU: * Burtin, A
EM: burtin@geologie.ens.fr
AF: Laboratoire de Géologie, École Normale Supérieure de Paris - CNRS, 24 rue Lhomond, Paris, 75005, France
AU: Bollinger, L
EM: laurent.bollinger@cea.fr
AF: Laboratoire de Détection et de Géophysique, CEA, BP12, Bruyères-le-Châtel, Bruyères, 91680, France
AU: Vergne, J
EM: vergne@geologie.ens.fr
AF: Laboratoire de Géologie, École Normale Supérieure de Paris - CNRS, 24 rue Lhomond, Paris, 75005, France
AU: Cattin, R
EM: cattin@geologie.ens.fr
AF: Laboratoire de Géologie, École Normale Supérieure de Paris - CNRS, 24 rue Lhomond, Paris, 75005, France
AU: Náb\v{e}lek, J L
EM: nabelek@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis, OR 97331, United States
AB: Analysis of continuous seismic data recorded by a passive seismological network (Hi-CLIMB) installed across the Himalayas reveals strong spatial and temporal variations in the ambient seismic energy produced at high frequencies (> 1 Hz). During the summer 2003, an increase of high-frequency seismic noise is observed for all the stations located along a steep narrow and deeply-incised channel of the Trisuli River, a major trans- Himalayan river. The summer growth in high-frequency energy is modulated by a 24-hour periodicity with minimum amplitude around noon and maximum late in the evening. The comparison of seismic noise amplitude with both regional meteorological and hydrological data along the river reveals clear correlations. Seasonal increase in ambient noise coincides with the strong Monsoon rainfall and a period of rapid melting of snow and ice in the high elevations. The observed 24-hour cyclicity is consistent with the daily fluctuation of the precipitation and river-discharge in the region. The observed river seismic noise is partly generated by stream turbulence but this mechanism fails to explain the noticed clockwise hysteresis of seismic noise amplitude versus water level. This pattern is better explained if a significant part of the observed seismic noise is caused by ground vibrations generated by bedload transport. Monitoring river bedload is essential to understand erosion processes and the evolution of bedload transport are valuable data difficult to acquire, especially during periods of flood crisis. Spectral analysis of background seismic noise could offer a great potential to safely quantify in continuous river bedload and monitor its spatial variations.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1817 Extreme events
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting