Geological evidences of surface rupture related to a seventeenth century destructive earthquake in Betic Cordillera (SE Spain): constraining the seismic hazard of the Alhama de Murcia fault

Abstract

Constraining the date of the last major event occurred in a fault is of paramount importance in probabilistic seismic hazard assessment when time-dependent models are considered. Eight of the twelve destructive earthquakes occurred in the eastern Betic Cordillera since 16 th century, are located less than 10 km away from the Alhama de Murcia fault (AMF). Up to now, it has not been identified any geological evidence on the ground surface to associate these events with the activity of specific fault sections of the AMF. In this work we present the first geological evidence of the catastrophic 1674 event occurred at Lorca (SE Spain). The excavations carried out at La Torrecilla creek exposed archaeological remains from the Arab period affected by 55±20 cm offset by the AMF fault. This event reached intensity VIII and produced 30 fatalities at Lorca for an estimated population of 7300 inhabitants. This supports the occurrence of earthquakes with surface rupture in the historical epoch on the Alhama de Murcia Fault and reinforces the results obtained in previous paleoseismological work. The theoretical scenarios of maximum magnitudes and recurrence time obtained by combining this historical event with the fault slip rate allow us to conclude that the seismic hazard associated with maximum magnitude events in this section could be high. In addition, the static Coulomb stress transferred to the Góñar-Lorca section by the 2011 (Mw 5.2) Lorca earthquake may have significantly increased the hazard.

Modelling earthquake rupture rates in fault systems for seismic hazard assessment: The Eastern Betics Shear Zone

“…4, the paleorate from Ortuño et al (2012) in AMF-1 is underestimated due to this effect, resulting in a misfit with the modelled MFDs of hyp. 1-3 and the paleorate by Martínez-Díaz et al (2018).…”

“…Contrarily, the EBSZ faults show many evidences of brittle deformation that splay upwards to the free surface, indicating rapid deformation (e.g. as seen in trenches by Ferrater, 2016;Martín-Banda et al, 2015;Martínez-Díaz et al, 2018). iii) There is no evidence of historical offsets, even small, in anthropic structures (walls, roads, etc.)…”

“…Most of the earthquakes in the EBSZ occur at depths <20 km (Martínez-Díaz, 1998) and some historical events are thought to be caused by its main faults (e.g. BSF for the 1829 Torrevieja event; Alfaro et al, 2012a or AMF for the 1674 Lorca event; Martínez-Díaz et al, 2018). Even though there are not known descriptions of surface ruptures during the historical period, paleoseismic studies have demonstrated the occurrence of at least one historical surface rupturing earthquake along the EBSZ (i.e.…”

“…More and higher precision paleoseismic parameters are available nowadays thanks to several paleoseismic studies conducted in the last decade (e.g. Ferrater, 2016;Insua-Arévalo et al, 2015;Martín-Banda et al, 2015;Martínez-Díaz et al, 2018). Recently, Rivas-Medina et al (2018) proposed a hybrid approach that avoids setting an arbitrary cut-off magnitude for distributing seismic moment between faults and zones and, at the same time, ensure that this distribution of seismic potential is not double-counted.…”

Pulverized quartz clasts in gouge of the Alhama de Murcia fault (Spain): Evidence for coseismic clast pulverization in a matrix deformed by frictional sliding

“…It is characterized by instrumental seismicity of moderate to low magnitude capable of producing catastrophic events (e.g., Rodríguez-Escudero et al, 2014). Historical and paleoseismic data show M w > 6.0 seismic ruptures during the Holocene (Martínez-Díaz et al, 2018).…”