Abstract
The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or ‘stable’ plate interiors, remains a subject of debate. Recent work in plate-boundary regions demonstrates the capacity for long-wavelength changes in continental water storage to produce observable surface deformation, induce crustal stresses and modulate seismicity rates. Here we show that a significant variation in the rate of microearthquakes in the intraplate New Madrid Seismic Zone at annual and multi-annual timescales coincides with hydrological loading in the upper Mississippi embayment. We demonstrate that this loading, which results in geodetically observed surface deformation, induces stresses within the lithosphere that, although of small amplitude, modulate the ongoing seismicity of the New Madrid region. Correspondence between surface deformation, hydrological loading and seismicity rates at both annual and multi-annual timescales indicates that seismicity variations are the direct result of elastic stresses induced by the water load.
Highlights
The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or ‘stable’ plate interiors, remains a subject of debate
We focus on the effect that annual and multi-annual variations in continentally stored water mass have on lithospheric deformation, and how this influences seismicity in intraplate North America
Despite the relatively small stress changes induced by annualscale water load variations, the annual variation of terrestrial water mass has been suggested to modulate ongoing seismicity in a number of active tectonic environments, in the Himalayas of Nepal[8,9,10], California[11,12,13] and beneath the Japanese Islands[14], by varying either the stress state on active faults or pore-fluid pressures at earthquake nucleation depths
Summary
The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or ‘stable’ plate interiors, remains a subject of debate. We demonstrate that this loading, which results in geodetically observed surface deformation on a centimetric scale, induces stresses within the lithosphere that, of small amplitude (1–2 kPa), are capable of modulating the ongoing seismicity of the New Madrid region.
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