Active faulting in the central Betic Cordillera (Spain): Palaeoseismological constraint of the surface-rupturing history of the Baza Fault (Central Betic Cordillera, Iberian Peninsula)

Abstract

This paper on the Baza Fault provides the first palaeoseismic data from trenches in the central sector of the Betic Cordillera (S Spain), one of the most tectonically active areas of the Iberian Peninsula. With the palaeoseismological data we constructed time-stratigraphic OxCal models that yield probability density functions (PDFs) of individual palaeoseismic event timing. We analysed PDF overlap to quantitatively correlate the walls and site events into a single earthquake chronology. We assembled a surface-rupturing history of the Baza Fault for the last ca. 45000 years. We postulated six alternative surface rupturing histories including 8-9 fault-wide earthquakes. We calculated fault-wide earthquake recurrence intervals using Monte Carlo. This analysis yielded a 4750-5150 yr recurrence interval. Finally, compared our results with the results from empirical relationships. Our results will provide a basis for future analyses of more of other active normal faults in this region. Moreover, our results will be essential for improving earthquakeprobability assessments in Spain, where palaeoseismic data are scarce.

Geometry and kinematics of the Baza Fault (central Betic Cordillera, South Spain): insights into its seismic potential

“…It must be highlighted that the obtained result is not the mean recurrence time for M max but for those surface rupture events that are represented in the palaeoseismological record. These values are similar to 4,750-5,150 years fault-wide earthquake recurrence intervals calculated using Monte Carlo analysis from palaeoseismic data (Castro et al, 2018). Figure 10 depicts the Probability Distribution Function (PDF) and the Cumulative Distribution Function (CDF) for the adjusted Weibull distribution using the computed parameters.…”

“…3), were deposited during the exorheic stage of the basin. Some of these recent deposits are offset by the BF (Castro et al, 2018).…”

“…The available palaeoseismological record (Castro et al, 2018) shows evidence of surface-rupture events in the past. Therefore, the recurrence time for these earthquakes has also been calculated.…”

“…45,000 BC and 1531 AD, including the historical 1531 AD Baza earthquake (Table 2). According to Castro et al (2018), the minimum magnitude for the earthquakes represented in the palaeoseismic record for the BF is around Mw 6. We have considered both the time and uncertainties (i.e.…”

“…On the contrary, recurrence intervals obtained from the palaeoseismological data may be underestimated. Palaeoseismological record of Castro et al (2018) is obtained from only 2 of the many strands of the BF. In addition, the paleoearthquake record is intrinsically incomplete, as it is likely that there are more paleoevents that have not been identified in the trenches because of the distributed character of the deformation along the BF strands.…”