Moment Tensor Inversion for the 5 July 1930 Montilla Earthquake (Southern Spain)

Abstract

The Iberia-Maghreb region, made up of Spain, Portugal, Algeria, and Morocco as well as the surrounding offshore areas in the Atlantic Ocean and Mediterranean Sea, is a complex plate boundary setting that displays important variations of earthquake faulting and stress patterns at regional and local scales ( e.g. , Buforn et al. 2004; Stich et al. 2006; Fernandez-Ibanez et al. 2007; De Vicente et al. 2008). The inventory of seismic moment tensors for the Iberia-Maghreb region is rapidly increasing as the network of seismic broadband stations is becoming denser, and small-to-moderate earthquakes can now be included in the analysis. Automated near real-time moment tensor inversion is implemented at the Instituto Geografico Nacional (IGN) (Rueda and Mezcua 2005), and the Instituto Andaluz de Geofisica (IAG) publishes processed moment tensor solutions, currently providing the largest regional catalog with 225 solutions to data (Stich et al. 2010). IAG source estimates are mainly for earthquakes since the mid 1990s; several older estimates (since 1980) can be found within routine larger-scale initiatives like the global CMT catalog ( Dziewonski and Woodhouse 1983). A less routine effort is source parameter retrieval from analog records for Iberia-Maghreb earthquakes that predate the era of digital seismogram recordings in order to supply faulting parameters and seismic moment for those historic earthquakes, particularly relevant for seismic hazard and/or seismotectonic studies (Pondrelli et al. 1999; Stich, Batllo et al. 2003; Stich et al. 2005; Batllo, Stich, Palombo et al. 2008). Here we report on source parameter retrieval for a damaging earthquake that struck the town of Montilla (near Cordoba, southern Spain) the night of 5 July 1930. The magnitude estimate for this earthquake is Ms = 5.1 (Karnik 1969), and its epicentral intensity Io has been evaluated as VIII (MSK). Just two contemporary studies describe this …