On 2 May 1977, a portable array of five stations was installed for the reconnaisance of the Alhama de Murcia fault in southern Spain. During this survey on 6 June 1977, a 4.2 mb (Lg) shock took place within the array and was followed by a long series of aftershocks. Due to the good quality of the records, a comprehensive study of location, magnitude, seismic moment, focal mechanism, and related parameters has been carried out. In the seismic moment calculation, we have used the coda wave analysis, which also gives information about Q values of approximately 320 and 617 for body and surface waves, respectively. In evaluating the focal mechanisms of the sequence, we have used a joint treatment which permits us to separate the two types of faulting involved in the rupture process. Finally, to interpret these results in terms of the tectonics of the region, the focal mechanism of the earthquake of 5 March 1981, which occurred in a neighboring area, has also been studied.