Circular 102—An instrumental study of New Mexico earthquakes July 1, 1964, through December 31, 1967

By A. R. Sanford and D. J. Cash, 1969, 7 pp., 3 tables, 1 fig. Supplement to circulars 78, 126, 171.

This circular describes the natural seismic activity within or very close to New Mexico during the period from July 1, 1964, through December 1, 1967. Origin times, locations, and magnitudes are listed for all earthquakes with magnitudes ³ 2.7. The most significant seismic event during the period of study was a magnitude 5.5 earthquake near Dulce on January 23, 1966. This earthquake (the strongest to occur in New Mexico for 28 years), with its aftershocks, accounts for more than half the total seismic activity during the 3½ year period. The remaining activity was broadly distributed over the state, with the strongest shocks coming from the northeastern quadrant.

In 1965, the NM Bureau of Mines and Mineral Resources published circular 78, which listed magnitudes and geographic locations of earthquakes that occurred within New Mexico from January 1, 1962, to July 1, 1964. All shocks during this time that could be located instrumentally are listed. Because the three New Mexico stations used in the study were distributed along the Rio Grande valley from Albuquerque to Las Cruces, the earthquakes reported are most numerous in the vicinity of these stations. Weak shocks near these stations were clearly recorded, whereas shocks of similar strength at considerable distances from the stations were either poorly recorded or not recorded at all. Thus the distribution of earthquake epicenters shown in Circular 78 are not completely accurate in siesmic representation.

Whenever available, origin times and epicenter coordinates reported by the U.S. Coast and Geodetic Survey have been used in this report. Two types of data distributed by the USCGS were consulted: (1) Preliminary Determination of Epicenters (PDE) reports and (2) Seismological Bulletins (MSI series). The PDE results are preliminary and do not always agree exactly with the data listed in the Seismological Bulletins. However, the latter bulletins are not available for approximately two years. To avoid this delay, the authors have relied on the PDE reports for the period October 1966 through December 1967.