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Earthquake scenario and probabilistic ground-shaking hazard maps for the Albuquerque-Belen-Santa Fe, New Mexico, corridor

New Mexico Geology

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Abstract

New Mexico's population is concentrated along the corridor that extends from Belen in the south to Espan??ola in the north and includes Albuquerque and Santa Fe. The Rio Grande rift, which encompasses the corridor, is a major tectonically, volcanically, and seismically active continental rift in the western U.S. Although only one large earthquake (moment magnitude [M] ??? 6) has possibly occurred in the New Mexico portion of the rift since 1849, paleoseismic data indicate that prehistoric surface-faulting earthquakes of M 6.5 and greater have occurred on average every 400 yrs on many faults throughout the Rio Grande rift. We have developed a series of nine scenario and probabilistic hazard maps that portray the ground shaking that could occur in the Albuquerque-Belen-Santa Fe corridor from future earthquakes in New Mexico. These maps, at a scale of 1:500,000, display color-contoured ground-motion values in terms of the parameters of peak horizontal acceleration and horizontal spectral accelerations at 0.2 and 1.0 second (sec) periods. The maps depict surficial ground shaking and incorporate the site-response effects at locations underlain by unconsolidated sediments. The scenario maps are for a M 7.0 earthquake rupturing the Sandia-Rincon faults, which are adjacent to and dip west beneath Albuquerque. The probabilistic maps are for the two annual exceedance probabilities of building code relevance, 10%, and 2% exceedance probabilities in 50 yrs (corresponding to return periods of 500 and 2,500 yrs, respectively). We included 57 Quaternary faults, all located within the Rio Grande rift, in the probabilistic seismic hazard analysis. These faults were characterized in terms of their geometry, rupture behavior (including possible segmentation), maximum expected earthquake magnitude, recurrence model, probability of activity, and slip rate, Preferred maximum magnitude values for these faults ranged from M 6.1 to 7.4 and preferred slip rates from 0.01 to approximately 0.12 mm/yr. Regional source zones and Gaussian smoothing of the historical seismicity were also included in the probabilistic hazard analysis to account for the hazard from background earthquakes (M ??? 6.5). A numerical ground-motion modeling approach and empirical attenuation relationships appropriate for extensional tectonic regimes were used to compute the scenario earthquake and probabilistic ground motions on rock. Amplification factors were then used to modify the rock motions and hence to incorporate site response into the hazard maps. These factors were based on three generalized geologic site-response categories (hard rock, soft rock, and firm/stiff soil) and were adopted from similar California-based categories because insufficient subsurface geologic and geotechnical data are available for the map area. The resulting hazard maps indicate that from both scenario and probabilistic perspectives, the ground-shaking hazard in the Albuquerque-Belen-Santa Fe corridor from future earthquakes could be severe, damaging, and potentially disastrous. In the event of a M 7.0 earthquake occurring on the Sandia-Rincon faults, ground shaking as characterized by peak ground acceleration could reach 0.7 g in much of the eastern half of the Albuquerque metropolitan area. (1 g = 980 cm/sec2, the rate of gravitational acceleration.) These high ground motions will be attributable to the city's location directly over the Sandia-Rincon faults and the amplifying effect of the unconsolidated sediments within the Albuquerque Basin. These levels of ground shaking will probably result in severe damage to traditional adobe construction and even to modern buildings. Long-period ground motions (> 1.0 sec), which are significant to long and tall structures (e.g., tall buildings, long bridges, and highway overpasses), will also be high (> 1.0 g). Injuries and loss of life will be likely. For the 500- and 2,500-yr return period maps, the highest peak accelerations are predicted to be at the d

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Earthquake scenario and probabilistic ground-shaking hazard maps for the Albuquerque-Belen-Santa Fe, New Mexico, corridor
Series title:
New Mexico Geology
Volume
26
Issue:
1
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
New Mexico Geology
First page:
3
Last page:
33
Number of Pages:
31