Lateral slip rate of Alhama de Murcia fault (SE Iberian Peninsula) based on a morphotectonic analysis: Comparison with paleoseismological data

Abstract

To define the seismic potential of the left-lateral strike-slip Alhama de Murcia fault (SE Iberian Peninsula), we calculated its slip rate by measuring offset linear features of known age using a morphotectonic analysis. The Lorca-Totana section of the fault yielded a minimum slip rate of 1.0 ± 0.2 mm/a for the past 30 ka, based on a channel whose age is estimated by OSL technique. The minimum left-lateral slip rate of the Goñar-Lorca section is 1.6-1.7 mm/a for the past 200 ka, based on eight offset surface channels, previously mapped alluvial fans dated by TL, and by new U-series dating of pedogenic carbonate. The U-series technique was used here for first time in the Iberian Peninsula to date small amounts (mg) of pedogenic carbonate. According to the newly estimated slip rate values, the Alhama de Murcia fault is one of the most active faults in the Eastern Betics Shear Zone. These values are larger and have fewer uncertainties in 1 comparison with previous slip rates estimations. In the Lorca-Totana section, the new lateral slip rate is compared with a slip rate calculated by means of a paleoseismic study showing good agreement between the values obtained with the two approaches.We encourage the combination of paleoseismology and morphotectonic analysis to obtain reliable slip rates for faults with scarce evidence of late Holocene slip.

How Much Nubia‐Eurasia Convergence Is Accommodated by the NE End of the Eastern Betic Shear Zone (SE Spain)? Constraints From GPS Velocities

“…We consider that all of the abovementioned evidence allows us to rule out the hypothesis of zero residual velocity for the Bajo Segura Basin. Likewise, the slip rates reported for the western and central sectors of the EBSZ range from 1.5 ± 0.3 to 0.8 ± 0.4 mm/year (Ferrater et al, ; Echeverria et al, , ; Martínez‐Díaz et al, , Gràcia et al, ; Moreno et al, , , among many others). Consequently, we postulate that the residual velocities obtained in the eastern EBSZ (our study area) should be similar to those reported in other sectors; that is, here, we discard the near‐zero hypothesis.…”

“…In addition, the study area is located in the EBSZ, which is a major tectonic structure with regional significance. Many geological (Ferrater et al, ; Martínez‐Díaz et al, ; Gràcia et al, ; Moreno et al, , , among many others) and geodetic (Echeverria et al, , ) studies have shown that the EBSZ is an active structure.…”

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

“…No paleoseismic trench studies are available for these faults. -AMF-1: The lateral slip rate in this section is inferred from offsets in fluvial channels summed for all the branches that the fault shows (Ferrater, 2016;Ferrater et al, 2017). Vertical slip rate estimations in this section are subject to a larger uncertainty and the values are about one order of magnitude lower (0.16-0.22 mm•yr −1 ; Ortuño et al, 2012), hence strike-slip is the predominant kinematics of the fault.…”

“…The minimum paleorates inferred from paleoseismic studies in this section are for the last 116 kyr (Ortuño et al, 2012). -AMF-2: The lateral slip rate (1.0 ± 0.2 mm•yr −1 ) is inferred from offsets in fluvial channels for the last 30 kyr (Ferrater, 2016;Ferrater et al, 2017). Paleoseismological 3D trenching in this section inferred net slip rate values in the same range (0.9 ± 0.1 mm•yr −1 for the last 20 kyr; Ferrater, 2016), hence verical slip rate is negligible (0.1 ± 0.0 mm•yr −1 ).…”

“…From a global perspective, it is an area with low-to-moderate seismicity. However, the slip rates estimated for some faults (> 1 mm•yr −1 ; Echeverria et al, 2015;Ferrater, 2016;Ferrater et al, 2017) underline the moderate-high seismic potential of the area and highlight the need to better constrain the probability of occurrence of potentially damaging earthquakes. The EBSZ is a complex faultsystem composed by an ensemble of faults with contrasting geometries and slip rate variations (Ferrater et al, 2017).…”