The 2012/2014 swarmquakes of Jaen, Spain: a working hypothesis involving hydroseismicity associated with the hydrologic cycle and anthropogenic activity

Abstract

A total of 2,300 swarmquake-type seisms have been striking the Torreperogil–Sabiote Hill (TSH) in southern Spain (Jaen) from October 2012 to the present, involving a major seismic crisis with six subseries until May 2013 (TSH seismic series, TSHS), followed by seven final series (FS). Two mild premonitory events occurred nearby in 2010–2011. Several evidences suggest cause–effect relationships between water and seismicity at the TSH: (1) The characteristics of seisms with a vast majority of ill-defined shallow/small events, spatial/temporal variations of the better constrained diffuse swarmquakes, increasing seismic velocities preceding stronger events, marked periodicities, abundant hydro-tremors, etc. (2) A series of spatial/temporal relationships between water and seismicity: Time lags between rainfall/reservoir peaks and seismic peaks; spatial links between swarmquakes and several factors (underground hydrogeology, reservoirs, etc.); etc. (3) From May 2013 to January 2014 evolution of rainfall and FS seismicity declined drastically at the same time. We suggest a hydroseismic hypothesis for TSH swarmquakes resulting from a complex series of cumulative factors: (1) A million-years natural setting involving geological, hydrogeological, geomorphological and tectonic elements. (2) A decades-long series of natural and anthropogenic factors are as follows: the 2012/2013 meteorological change, the massive overexploitation of the confined aquifers and alternating impoundment/emptying of the Giribaile reservoir.