Tectonic evolution of the Lorca sector from the Late Miocene to the Quaternary

Abstract

The Alhama de Murcia Fault presents several parallel surfaces, forming a wide fault zone. Even at distances of several km, there are other faults belonging to the same system. These faults created subsidiary structures, some of kilometric lengths, as in the case of the progressive uplift of the Peña Rubia sector, occurring from the end of the Middle Miocene. Later and partially coeval, was the formation of the Castillo antiform. The sinistral displacement of the large Alhama de Murcia Fault and that of smaller dextral conjugated faults was caused by stress from a nearly N-S compression and a related perpendicular extension. At some points in time, the positions of σ1 and σ2 axes switched, permitting normal movements, particularly in faults with approximately N-S directions, and hence raising the possibility of this type of focal mechanism in some earthquakes.The NE border of Peña Rubia (on the eastern end of Sierra de Las Estancias), also the SE border of the Lorca Basin, is affected by small (compared with the main ones) strike-slip and reverse faults that are also consistent with the palaeostress deduced. Nevertheless, along this border no significant or continuous fault is detected.