PROBABILISTIC SEISMIC HAZARD IN NEW MEXICO AND BORDERING AREAS BASED ON EARTHQUAKE ACTIVITY: 1962-1998

Probabilistic seismic hazard maps for New Mexico and bordering areas based on instrumental data collected from 1962-1998 are presented in terms of peak horizontal ground accelerations at 10% and 2% probability of exceedance in a 50-year period, 500 year and 2500 year return periods, respectively. The 500 year return period hazard map shows moderate to low seismic hazards on firm ground with the highest level of ground acceleration, ~0.18g, in the central Rio Grande Valley near Socorro. Along the major population corridor of the state from Albuquerque to Santa Fe, the peak ground acceleration is ~0.08g. The cumulative contribution curves for selected areas show that earthquakes of magnitude less than 6.0 contribute the most to seismic hazards. Structural damage is not expected to modern buildings on firm ground for earthquakes in this strength range but non-structural damage can be significant.

Sensitivity studies for the probabilistic seismic hazard analyses indicate that the hazard estimates for New Mexico are stable. Among controlling factors, the b-value in the recurrence model is the most important factor for estimating rates for earthquakes in the magnitude range 4.0 to 6.5. Pre-instrumental data from 1850-1961 are in reasonably good agreement with the rate based on instrumental data from 1962-1998. Absence of reports of damage to Pueblo Indian structures (1300 AD to present) and Spanish Colonial missions, churches, and haciendas (1600 AD to 1850 AD) suggests a level of earthquake activity similar to historical seismicity (1850 AD to present) for the Rio Grande valley population corridor extending from Socorro through Albuquerque and Santa Fe to Taos.