How Droughts Influence Earthquakes

Abstract

This study formulates co-seismic conditions involving three specific angles that relate to balancing of the magnitude and direction of the associated forces that collectively when perturbed can precipitate an earthquake event. The hypothesis developed in this research (1) Enlarges our knowledge base by extending the canonical frictional phenomena into fatigue conditions at the plate interface; 2) Indicates that large scale, extended droughts, by exerting cyclical unloading, create two mechanisms for enhancing tectonic instability and the associated triggering earthquakes; and (3) Integrates the role of (generic) groundwater fluctuations at the nexus thereby linking climate change caused extremes and perturbations of the tectonic earthquake cycle. With this hypothesis, mechanics-based process modelling has the potential to be used to determine the locations and development of the evolving regional stresses and to answer the questions of why, when and how extreme will be a specific earthquake event.

Correction of GRACE measurements of the Earth’s moment of inertia (MOI)

“…Importantly, both solutions suggest a steady, statistically robust rate of MOI increase, passing a two-tailed t-test with p = 0.04 for dof = 15, that reaches ~ 10.1 × 10 27 kg m 2 /year, which is equivalent to a 10.91 μs/ year increase in the length of a day, during 2002-2017. In particular, the short-term spikes associated with hydrological patterns linked with major earthquakes [e.g., the 2006 spike associated with the Nepal earthquakes, Ren and Fu (2019)] agree very well. Repeating the above analyses using the CSR mascon solutions suggest, qualitatively, the same conclusions as those from the JPL mascon solutions.…”

“…Instead of the relocation of crust and upper mantle material, it is the associated groundwater, or precipitation redistribution, that dominate the MOI fluctuations. This may be another facet of the relation between droughts and major earthquakes (Ren and Fu 2019). Notably, the dynamic nature of permeability, as revealed by co-seismic and post-seismic hydrologic phenomena (Ingebritsen et al 2006), has implications for groundwater systems in the fault vicinity.…”