Hydrologic Responses to Earthquakes and a General Metric

Abstract

Hydrologic responses to earthquakes, including liquefaction, changes in stream and spring discharge, changes in the properties of groundwater such as geochemistry, temperature and turbidity, changes in the water level in wells, and the eruption of mud volcanoes, have been documented for thousands of years. Except for some water-level changes in the near field which can be explained by poroelastic responses to static stress changes, most hydrologic responses, both within and beyond the near field, can only be explained by the dynamic responses associated with seismic waves. For these responses, the seismic energy density e may be used as a general metric to relate and compare the various hydrologic responses. We show that liquefaction, eruption of mud volcanoes and increases in streamflow are bounded by e $ 10 )1 J m )3 ; temperature changes in hot springs are bounded by e $ 10 )2 J m )3 ; most sustained groundwater changes are bounded by e $ 10 )3 J m )3 ; geysers and triggered seismicity may respond to seismic energy density as small as 10 )3 and 10 )4 J m )3 , respectively. Comparing the threshold energy densities with published laboratory measurements, we show that undrained consolidation induced by dynamic stresses can explain liquefaction only in the near field, but not beyond the near field. We propose that in the intermediate field and far field, most responses are triggered by changes in permeability that in turn are a response to the cyclic deformation and oscillatory fluid flow. Published laboratory measurements confirm that changes in flow and time-varying stresses can change permeability, inducing both increases and decreases. Field measurements in wells also indicate that permeability can be changed by earthquakes in the intermediate field and far field. Further work, in particular field monitoring and measurements, are needed to assess the generality of permeability changes in explaining far-field hydrologic responses to earthquakes.

Triggering of the largest Deccan eruptions by the Chicxulub impact

“…The amount of seismic energy dissipated by seismic waves has thus been proposed as a measure that may be correlated with triggered eruptions (Wang and Manga, 2010):…”

Hydrological effects of theMW7.1 Darfield (Canterbury) earthquake, 4 September 2010, New Zealand

“…Responding equally to PGA of 5 )10 (5 g The magnitude of the maximum change in groundwater level (positive or negative, coseismic or post-seismic) shows a negative correlation with distance from the earthquake epicentre ( Fig. 6C; see also Wang & Manga 2010b). To compare hydrologic responses with a measure of seismic shaking intensity, the magnitude of the maximum groundwater level change was plotted against the PGA measured at the nearest GeoNet strong motion seismometer ( Fig.…”

Changes in hot spring temperature and hydrogeology of the Alpine Fault hanging wall, New Zealand, induced by distal South Island earthquakes

“…During the Mw7.8 Dusky Sound earthquake, there were clear offsets *Estimated-PGV max times the shear modulus (3 9 10 10 Pa), divided by shear wave velocity (3.5 km sec À1 ). † Seismic energy density after Wang & Manga (2010b).…”