Discriminating between natural and anthropogenic earthquakes: insights from the Emilia Romagna (Italy) 2012 seismic sequence

Abstract

The potential for oilfield activities to trigger earthquakes in seismogenic areas has been hotly debated. Our model compares the stress changes from remote water injection and a natural earthquake, both of which occurred in northern Italy in recent years, and their potential effects on a nearby Mw 5.9 earthquake that occurred in 2012. First, we calculate the Coulomb stress from 20 years of fluid injection in a nearby oilfield by using a poroelastic model. Then, we compute the stress changes for a 2011 Mw 4.5 earthquake that occurred close to the area of the 2012 mainshock. We found that anthropogenic activities produced an effect that was less than 10% of that generated by the Mw 4.5 earthquake. Therefore, the 2012 earthquake was likely associated with a natural stress increase. The probability of triggering depends on the magnitude of recent earthquakes, the amount of injected water, the distance from an event, and the proximity to the failure of the activated fault. Determining changes that are associated with seismic hazards requires poroelastic area-specific models that include both tectonic and anthropogenic activities. This comprehensive approach is particularly important when assessing the risk of triggered seismicity near densely populated areas.

Finite Element Modelling of Coupled Fluid-Flow and Geomechanical Aspects for the Sustainable Exploitation of Reservoirs: The Case Study of the Cavone Reservoir

“…In both cases, the major pressure's increase has been detected near well C014, the main injector of the field, while the pressure's decreases have been measured near wells C007, C009, and C017. The prominent influence on pressure changes induced by the production activity of well C014 was also fully recognized and investigated by Albano et al [9]. Though we represent wells as production-injection lines and not as point sources, the obtained pressure values fit with those of the Cavone report [7].…”

“…Considering that typically the friction coefficient µ s varies in the interval 0.6-0.85, and that the choice of low µ s values is conservative [31], µ s has been assumed equal to 0.6 [32]. Because no information about Skempton's and Biot's coefficients were available, the values of 1 and 0.8, respectively, were set [9].…”

“…To this purpose, the reservoir was analyzed as a three-dimensional model where injection and production zones were implemented as point sources sunk in a half-space overlain by an impermeable layer. More recently, Albano et al [9] compared the stress changes from water injection at the Cavone reservoir and its potential effects on 2012 Emilia earthquake by means of a two-dimensional finite element code.…”

Did Anthropogenic Activities Trigger the 3 April 2017 Mw 6.5 Botswana Earthquake?

“…The potential for anthropogenic activities to trigger earthquakes has been widely acknowledged by the scientific community [31][32][33][34]. In particular, the generation mechanisms and magnitudes of anthropogenic earthquakes depend on several factors, such as the volume of the injected or extracted fluids, the extent of the perturbation [35], the geometry and orientation of the fault planes, the hydraulic connection between the injection and extraction zones and the fault planes [14], the magnitude of the tectonic stress field, and the distance between anthropogenic activities and earthquake source.…”

Structural and Stratigraphic Control on Salient and Recess Development Along a Thrust Belt Front: The Northern Apennines (Po Plain, Italy)

“…Three different arcs have been recognized along the thrust front: the Monferrato, the Cremona, and the Ferrara arcs (see Consiglio Nazionale delle Ricerche, ). The accretionary prism front is seismically active (Albano et al, ; Benedetti et al, ; Boccaletti, Corti, & Martelli, ; Bonini et al, ; DISS Working Group, ; Govoni et al, ; Lavecchia et al, ; Michetti et al, ; Toscani et al, ; Turrini et al, ; Vannoli et al, , and references therein). Before the M L 5.9, 20 May 2012 Emilia earthquake, the area was characterized by low strain rate, which potentially indicates a greater likelihood for more numerous and larger earthquakes (Cuffaro et al, ; Doglioni et al, , ; Riguzzi et al, ).…”