Seismogenic zonation and seismic hazard estimates in a Southern Italy area (Northern Apulia) characterised by moderate seismicity rates

Abstract

Abstract. The northernmost part of Apulia, in Southern Italy, is an emerged portion of the Adriatic plate, which in past centuries was hit by at least three disastrous earthquakes and at present is occasionally affected by seismic events of moderate energy. In the latest seismic hazard assessment carried out in Italy at national scale, the adopted seismogenic zonation (named ZS9) has defined for this area a single zone including parts of different structural units (chain, foredeep, foreland). However significant seismic behaviour differences were revealed among them by our recent studies and, therefore, we re-evaluated local seismic hazard by adopting a zonation, named ZNA, modifying the ZS9 to separate areas of Northern Apulia belonging to different structural domains. To overcome the problem of the limited datasets of historical events available for small zones having a relatively low rate of earthquake recurrence, an approach was adopted that integrates historical and instrumental event data. The latter were declustered with a procedure specifically devised to process datasets of low to moderate magnitude shocks. Seismicity rates were then calculated following alternative procedural choices, according to a "logic tree" approach, to explore the influence of epistemic uncertainties on the final results and to evaluate, among these, the importance of the uncertainty in seismogenic zonation. The comparison between the results obtained using zonations ZNA and ZS9 confirms the well known "spreading effect" that the use of larger seismogenic zones has on hazard estimates. This effect can locally determine underestimates or overestimates by amounts that make necessary a careful reconsideration of seismic classification and building code application.

Seismicity in northeast edge of the Mexican Volcanic Belt (MVB), activation of an undocumented fault: the Peñamiller earthquake sequence of 2011, Queretaro, Mexico

“…In order to enrich seismic information for this type of faulting to gain more insight into the tectonic situation and of the seismic risk of the region, such as occur in others world regions (e.g. Polonia et al, 2012;Vipin et al, 2009;Del Gaudio et al, 2009). In this work is carried out a detailed analysis of the seismic source parameters of events of the Peñamiller sequence, monitored during the first three months of 2011. consisted on the identification of the origin of the activity and the estimation of seismic source parameters, in order to analyze and associate its occurrence with the regional tectonic regime of the MVB.…”

Seismicity at the northeast edge of the Mexican Volcanic Belt (MVB) and activation of an undocumented fault: the Peñamiller earthquake sequence of 2010–2011, Querétaro, Mexico

“…Examples of similar documented events in other parts of the world where the seismic activity is too low are given in Polonia et al (2012), Vipin et al (2009) andDel Gaudio et al (2009). In this study we present a detailed analysis of the seismic source parameters of events of the Peñamiller sequence, monitored during the first three months of 2011.…”