The ages of nine alluvial units, identified by the integration of data obtained from five trenches at the southern termination of the Alhama de Murcia Fault (AMF) (eastern Betics, Spain), are ...constrained using luminescence dating based on the Optically Stimulated Luminescence (OSL) from quartz, Infrared Stimulated Luminescence (IRSL) at 50°C, and post‐IR elevated temperature (225°C) IRSL signals from K‐feldspar. All signals pass the routine tests associated with the Single Aliquot Regenerative (SAR) protocol, including the recycling ratio, recuperation, and dose recovery tests. The equivalent doses (De), residual doses and anomalous fading rates (‘g’‐values) of the IRSL at 50°C (IR50) and post‐IR IRSL at 225°C (pIRIR225) from K‐feldspar are compared for 16 samples. The residual doses in laboratory‐bleached samples suggest that there is no significant unbleachable residual dose using these signals; the residual doses are 0.17±0.15 Gy and 0.93±0.80 Gy, respectively. For both signals, the residual doses appear to depend on the corresponding natural doses; that is, the larger the natural doses, the larger the residuals, an observation made for the first time for IRSL signals. The average fading rate for the pIRIR225 (0.94±0.07%/decade, n = 48) is markedly lower than that for IR50 (2.08±0.16%/decade, n = 48), indicating that the age correction for the pIRIR225 is much smaller than that for IR50. The agreement between the quartz OSL, corrected IR50, and corrected pIRIR225 for the two youngest samples suggests that the pIRIR225 is an accurate dating signal in this age range (<25 ka). The oldest age obtained using the corrected pIRIR225 signal is 320±20 ka for sample 098807; the corrected IR50 age is only 154±15 ka. Although this suggests that the pIRIR225 signal circumvents the effect of anomalous fading to a great extent, the resulting age cannot be regarded as necessarily accurate because of the limitations of the fading correction model used, and the absence of independent age control for the old samples. Nevertheless, our luminescence ages provide the first age constraints on the seismic activity of the southern termination of the AMF.
On May 11th 2011, a Mw 5.2 earthquake stroke the city of Lorca in the SE Spain. This event caused 9 fatalities, 300 injuries and serious damage on the city and the surrounding areas. The Lorca ...earthquake occurred in the vicinity of a region bounding two well-known segments of a large active fault, the Alhama de Murcia fault (AMF). The Lorca earthquake offers a unique opportunity to study how strain is accommodated in an intersegment region of a large strike slip fault. We map recent tectonic structures in the epicentral region and we use radar interferometry to analyze the coseismic deformation. Combining these data with seismological observations of Lorca seismic sequence we first model the source of the earthquake. Then we analyze the influence of our preferred model in the adjacent segments by Coulomb failure stress modeling. The proposed earthquake source model suggests that this event ruptured an area of ~4×3km within the complex structure that limits the Goñar–Lorca and Lorca–Totana segments of the AMF. The induced static stress change on the adjacent segments of the fault represents a seismic cycle advance equivalent to 200 to 1000years of tectonic loading.
► We analyze the source and the coseismic deformation produced by the Lorca Earthquake. ► The earthquake was produced by the Alhama de Murcia Fault. ► Lorca earthquake ruptured an area of by 4×3km within an intersegment region. ► Lorca intersegment zone may act with a characteristic seismogenic behavior.
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