Receiver functions at three broad-band stations located in the most easterly Inner Betics have been analyzed to investigate the structure of its underlying crust and uppermost mantle. These stations are located within a geologically distinctive block bounded by the Palomares/Alhama de Murcia faults, which is characterized by high heat-flow values, widespread strike-slip faulting and Neogene volcanism. Our analysis shows that a low velocity zone pervades the uppermost mantle beneath the stations, and that the overlying crust has a high Vp/Vs ratio and a prominent intracrustal low velocity zone (i) between the Palomares and Alhama de Murcia faults and (ii) east of Murcia, perhaps thermally perturbing the upper crust north and east of Cartagena. Independent studies show that the seismic velocities of the intervening mantle lid are normal beneath the stations, and we suggest that our observations result from rapidly ascending magma diapirs ponding at intracrustal levels within the distinctive block.