Approach for combining fault and area sources in seismic hazard assessment: application in south-eastern Spain

Abstract

Abstract. This paper presents a methodological approach to seismic hazard assessment based on a hybrid source model composed of faults as independent entities and zones containing residual seismicity. The seismic potential of both types of sources is derived from different data: for the zones, the recurrence model is estimated from the seismic catalogue. For fault sources, it is inferred from slip rates derived from palaeoseismicity and GNSS (Global Navigation Satellite System) measurements. Distributing the seismic potential associated with each source is a key question when considering hybrid zone and fault models, and this is normally resolved using one of two possible alternatives: (1) considering a characteristic earthquake model for the fault and assigning the remaining magnitudes to the zone, or (2) establishing a cut-off magnitude, Mc, above which the seisms are assigned to the fault and below which they are considered to have occurred in the zone. This paper presents an approach to distributing seismic potential between zones and faults without restricting the magnitudes for each type of source, precluding the need to establish cut-off Mc values beforehand. This is the essential difference between our approach and other approaches that have been applied previously. The proposed approach is applied in southern Spain, a region of low-to-moderate seismicity where faults move slowly. The results obtained are contrasted with the results of a seismic hazard method based exclusively on the zone model. Using the hybrid approach, acceleration values show a concentration of expected accelerations around fault traces, which is not appreciated in the classic approach using only zones.

A sanity check for earthquake recurrence models used in PSHA of slow deforming regions: the case of SW Iberia

“…In the examples investigated only area earthquake source zones were tested but the methodology can be easily extended to PSHA studies that use more detailed source parametrization (e.g. Rivas-Medina et al, 2018). When logic tree and/or Monte-Carlo methods are used to characterize the epistemic and aleatoric uncertainties in PSHA, it is recommended that the outcome of the sanity tests should be used on a weighing scheme, as it is already used in probabilistic tsunami hazard assessment (Davies et al, 2017, Basili et al, 2019.…”

“…Zitellini et al, 2009;Custódio et al, 2015;Neres et al, 2016), as detailed in section 2. Recently, in smaller domains where the fault geometry and activity are considered to be well known, like in SE Spain, a mixed source model has been proposed (Rivas-Medina et al, 2018) where the earthquake potential is distributed between the faults and the zone. This is an exceptional case that cannot be extended to the whole W and SW Iberia.…”

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

“…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. This is achieved by computing and distributing the seismic potential between faults and zones using the events contained in the completeness period of the catalogue for different magnitude ranges.…”

Recurrence times of central‐southern Apennine faults (Italy): Hints from palaeoseismology

“…Wiemer & Wyss, 1993), one of the most important and often exclusive result provided by palaeoseismology is the direct measurement of the time interval of consecutive fault ruptures, a critical factor in seismic risk evaluation. This is a crucial item in those regions for which the brevity of the continuous historical record, and/or the slow slip rates of seismogenic faults, make determination of earthquake recurrence from geological evidence the only way for performing hybrid regional seismic hazard analysis (Rivas‐Medina, Benito, & Gaspar‐Escriban0 J.M., 2018; Wu, Cornell, & Winterstein, 1995).…”