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Titolo:
Rapid fluid disruption: A source for self-potential anomalies on volcanoes
Autore:
Johnston, MJS; Byerlee, JD; Lockner, D;
Indirizzi:
US Geol Survey, Menlo Park, CA 94025 USA US Geol Survey Menlo Park CA USA94025 l Survey, Menlo Park, CA 94025 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B3, volume: 106, anno: 2001,
pagine: 4327 - 4335
SICI:
0148-0227(20010310)106:B3<4327:RFDASF>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
LA-FOURNAISE VOLCANO; OSHIMA VOLCANO; JAPAN; FLOW; EARTHQUAKES; RESISTIVITY; EMISSIONS; PRESSURE; ERUPTION; SYSTEMS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Byerlee, JD US Geol Survey, 345 Middlefield Rd,MS977, Menlo Park, CA 94025USA US Geol Survey 345 Middlefield Rd,MS977 Menlo Park CA USA 94025
Citazione:
M.J.S. Johnston et al., "Rapid fluid disruption: A source for self-potential anomalies on volcanoes", J GEO R-SOL, 106(B3), 2001, pp. 4327-4335

Abstract

Self-potential (SP) anomalies observed above suspected magma reservoirs, dikes, etc., on various volcanoes (Kilauea, Hawaii; Mount Unzen, Japan; Piton de la Fournaise, Reunion Island, Miyake Jima, Japan) result from transient surface electric fields of tens of millivolts per kilometer and generallyhave a positive polarity. These SP anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained. We propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization/disruption. As liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions, both charge generation and local. increase in electrical resistivity by removal of fluids should occur. We report laboratory observations of electric fields in hot rock samples generated by pulses of fluid (water) through the rock at atmospheric pressure. These indicate the relative amplitudes of rapid fluid disruption (RFD) potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign. Above vaporization temperatures, RFD effects of positive sign in the direction of gas flow dominate, whereas below these temperatures, effects of negative sign dominate. This suggests thatthe primary contribution to observed self-potential. anomalies arises fromgas-related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport. At lower temperatures, the primary contribution is from electrokinetic effects modulated perhaps by changingelectrical resistivity and RFD effects from high-pressure but low-temperature CO2 and SO2 gas flow ripping water molecules from saturated crustal rocks. If charge generation is continuous, as could well occur above a newly emplaced dike, positive static potentials will be set up that could be sustained for many years, and the simplest method for identifying these hot, active regions would be to identify the SP anomalies they generate.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 12/08/20 alle ore 20:22:58