River thorium concentrations can record bedrock fracture processes including some triggered by distant seismic events

Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace...

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Published inNature communications Vol. 14; no. 1; p. 2395
Main Authors Gilbert, Benjamin, Carrero, Sergio, Dong, Wenming, Joe-Wong, Claresta, Arora, Bhavna, Fox, Patricia, Nico, Peter, Williams, Kenneth H.
Format Journal Article
LanguageEnglish
Published London Nature Publishing Group UK 26.04.2023
Nature Publishing Group
Nature Portfolio
Subjects
704/2151/241
704/2151/508
704/47/4112
Arsenic
Bedrock
Beryllium
Dilution
Earthquakes
Fractures
Frequency measurement
Geochemistry
Geophysical methods
GEOSCIENCES
Groundwater
Humanities and Social Sciences
Hydrology
multidisciplinary
Rivers
Science
Science (multidisciplinary)
Seismic activity
Solutes
Statistical correlation
Thorium
Trace elements
Watersheds
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Summary:Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace element thorium (Th) can provide a signature of bedrock fracture processes spanning neighboring watersheds in Colorado. River Th concentrations show abrupt (subdaily) excursions and biexponential decay with approximately 1-day and 1-week time constants, concentration patterns that are distinct from all other solutes except beryllium and arsenic. The patterns are uncorrelated with daily precipitation records or seasonal trends in atmospheric deposition. Groundwater Th analyses are consistent with bedrock release and dilution upon mixing with river water. Most Th excursions have no seismic signatures that are detectable 50 km from the site, suggesting the Th concentrations can reveal aseismic fracture or fault events. We find, however, a weak statistical correlation between Th and seismic motion caused by distant earthquakes, possibly the first chemical signature of dynamic earthquake triggering, a phenomenon previously identified only through geophysical methods. Daily measurements of the river concentration of the ultra-trace element thorium (Th) can provide a novel signature of bedrock fracture processes
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AC02-05CH11231
USDOE Office of Science (SC), Biological and Environmental Research (BER)
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-023-37784-3