Bayesian Detection of Streamflow Response to Earthquakes

Abstract

Pliny the Elder lived in the 1st century CE and was among the first to report in writing that the amount of water discharged at Earth's surface can change following earthquakes. Following the Great Lisbon Earthquake in 1755, Immanuel Kant described sudden changes in surface hydrology that occurred "in the same minutes as the earthquake devastated the coasts of Portugal." He noted that "in just (…) minutes, the mineral water at Töplitz in Bohemia (Czech Republic) suddenly stopped and returned to blood red," while "in the Kingdom of Fez (Morocco) in Africa, a subterranean force split a mountain and poured blood-red streams out of its mouth" (Kant, 1756). Many other similar observations show that streamflow can increase or decrease following strong seismic shaking and thus reflects responses of groundwater being supplied to streams (Mohr et al., 2017). Earthquakes modify crustal stresses, hydraulic heads, and physical properties such as the permeability of the subsurface that all control water flux (Wang & Manga, 2014). Altered river discharges following earthquakes have been reported in the near-and intermediate-field, that is, within one or a few rupture lengths away from the earthquake source (Rojstaczer et al., 1995). The magnitude of streamflow responses can involve the release of >1 km 3 of excess water into streams (Mohr et al., 2017) and sustain enhanced streamflow for months (