Caracterización estructural de la falla activa de Baza (sur de España). Implicaciones en el SHA

Abstract

The Baza Fault (BF) is one of the most active structures in the Central Betic Cordillera (Spain). This normal fault is the seismogenic source of the destructive Mms ca. 6.3, 1531 AD Baza earthquake, and has a surface rupture history of 8 to 9 palaeoevents during the last 45 Kyr. Geodesic slip rates for the BF range between 0.3±0.3 mm/yr and 1.3±0.4 mm/yr, and geological-geomorphological slio rates range between 0.2-0.7 mm/yr. In this work we characterize and analyze the structure of the BF (geometry and kinematics) combining both surface (field observations) and sub-surface (seismic and gravity profiles) data. The BF is a ca. 37 km, normal fault dipping ~55° to the east. We distinguish between two fault sections based on along-strike variations in the BF geometry: a narrow NNW-SSE striking north section and a NW-SE striking south section that widens southwards. These geometric and kinematic features obtained from our structural characterization together with data from previous stu- dies, allow us to evaluate the seismogenic potential of the BF. Seismic fault segmentation is discussed using geometrical and geological criteria. In this analysis, we model several fault displacement scenarios for the 1531 AD event (partial and total fault ruptures) and compare the results with the recorded historical damage distribution. After defining fault sections, we calculate the parameters that will express the seismogenic potencial of the BF: maximum expected magnitudes, recurrence intervals, and probabilities of occurrence.