Circular 126—Instrumental study of New Mexico earthquakes January 1968 through June 1971

By T. R. Toppozada and A. R. Sandford, 1972, 6 pp., 3 tables, 1 fig.

Supplement to circulars 78, 102, 171. A total of 19 earthquakes are listed, 11 located by the National Earthquake Information Center and eight by the New Mexico Institute of Mining and Technology. Origin times, magnitudes, and locations are given for all earthquakes having local magnitudes ³ 2.7. A total of 19 earthquakes are listed, 11 located by the National Earthquake Information Center and eight by the New Mexico Institute of Mining and Technology. Arrival times for shocks located by NMIMT are given. During this 3½ year interval the earthquake epicenters were concentrated in the vicinity of the Rio Grande valley. This distribution of seismic activity is in better agreement with the historical record of felt shocks than was the distribution obtained from the preceding six years of instrumental data.

This circular reports the natural seismic activity in, and bordering, New Mexico for the period January 1, 1968 through June 30, 1971. Earlier published studies on earthquakes in the state, based on instrumental data, cover the periods January 1, 1962 through June 30, 1964. The earthquake locations, origin times, and magnitudes listed are from two sources: (1) reports published by the National Earthquake Information Center, Environmental Research Laboratories, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, and (2) studies by the NMIMT. The principal stations used in the NMIMT study are located at Socorro and Albuquerque. Because of the location of these seismic stations, weak shocks in the central part of the state can be located with relative ease whereas earthquakes of similar strength located in the far corners of the state may not be clearly recorded at a sufficient number of stations for a location. To obtain a geographical distribution of seismic activity free of any station location bias, only shocks with local magnitudes ³ 2.7 have been tabulated. If any shocks of this strength have been missed it would be because of their location in the remotest areas of the state.