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Recent leveling conducted by the National Geodetic Survey in central New Mexico provides new evidence of ongoing tectonic deformation associated with the Rio Grande rift. A 1980-1981 resurvey over suspected midcrustal and shallow magma bodies near Socorro, New Mexico, indicates continued uplift averaging 0.18 cm/yr between 1951 and 1980. Although this rate is somewhat smaller than that reported previously (0.34 cm/yr between 1912 and 1951), the new observations suggest possible systematic errors in the earlier surveys. Reanalysis of the earlier data gives an average rate of 0.23 cm/yr from 1912 to 1951, consistent not only with the new releveling observations but also with geomorphic evidence which indicates an average uplift rate of 0.18 cm/yr over the past 20,000 years. Thus the rate of uplift may be relatively constant. The new releveling measurements also confirm prominent zones of subsidence flanking the central uplift. Modeling the deformation, together with other geophysical observations, suggests that the movements in the Socorro area are likely associated with the 19-km-deep Socorro magma body. Although the details of magma movements are not well constrained, plausible models include flow of magma from the periphery toward the central magma chamber and flow from sources in the lower crust into the midcrust. Horizontal strain calculated for these models is generally consistent with the small strain reported from repeated trilateration surveys in the Socorro area. The Rio Grande rift is clearly an important site for future monitoring of crustral deformation. INTRODUCTION AND GEOLOGIC SETTING Geophysical and geological observations indicate the existence of magma at intermediate and shallow depths in the crust beneath the Rio Grande rift in the vicinity of Socorro, New Mexico [Sanford et al., 1973, 1977a, b; Sanford, 1983; Brown et al., 1979; Shuleski, 1976; Johnston, 1978; Roach, 1982]. The most prominent magma body lies at a depth of 19-20 km and has the shape of a thin sill with a minimum areal extent of 1700 km 2 [Rinehart et al., 1979]. In addition, shallow magma intrusions predominantly between 5 and 10 km below the surface have been inferred from m,•croearthquake seismograms [e.g., Sanford, 1983]. Evidence that the magma bodies are currently active includes (1) anomalously high earthquake activity (including swarms) in the Albuquerque to Socorro section of the rift, as compared to other parts of the rift [Sanford et al., 1979, 1981], (2) geomorphic and other geologic evidence for post-Pliocene activity in the Socorro area [Sanford et al., 1972; Chapin and Seager, 1975; Bachman and Mehnert, 1978; Ouchi, 1983-1, and (3) geodetic evidence for historic crustal deformation above the magma body [Reilinger and Oliver, 1976; Reilinger et al., 1980]. This paper reports and interprets new leveling measure-ments conducted in 1980 and 1981 by the National Geodetic Survey (NGS) in the Socorro area of the Rio Grande rift. The new observations confirm previously published results of crustal uplift apparently relate...
Recent leveling conducted by the National Geodetic Survey in central New Mexico provides new evidence of ongoing tectonic deformation associated with the Rio Grande rift. A 1980-1981 resurvey over suspected midcrustal and shallow magma bodies near Socorro, New Mexico, indicates continued uplift averaging 0.18 cm/yr between 1951 and 1980. Although this rate is somewhat smaller than that reported previously (0.34 cm/yr between 1912 and 1951), the new observations suggest possible systematic errors in the earlier surveys. Reanalysis of the earlier data gives an average rate of 0.23 cm/yr from 1912 to 1951, consistent not only with the new releveling observations but also with geomorphic evidence which indicates an average uplift rate of 0.18 cm/yr over the past 20,000 years. Thus the rate of uplift may be relatively constant. The new releveling measurements also confirm prominent zones of subsidence flanking the central uplift. Modeling the deformation, together with other geophysical observations, suggests that the movements in the Socorro area are likely associated with the 19-km-deep Socorro magma body. Although the details of magma movements are not well constrained, plausible models include flow of magma from the periphery toward the central magma chamber and flow from sources in the lower crust into the midcrust. Horizontal strain calculated for these models is generally consistent with the small strain reported from repeated trilateration surveys in the Socorro area. The Rio Grande rift is clearly an important site for future monitoring of crustral deformation. INTRODUCTION AND GEOLOGIC SETTING Geophysical and geological observations indicate the existence of magma at intermediate and shallow depths in the crust beneath the Rio Grande rift in the vicinity of Socorro, New Mexico [Sanford et al., 1973, 1977a, b; Sanford, 1983; Brown et al., 1979; Shuleski, 1976; Johnston, 1978; Roach, 1982]. The most prominent magma body lies at a depth of 19-20 km and has the shape of a thin sill with a minimum areal extent of 1700 km 2 [Rinehart et al., 1979]. In addition, shallow magma intrusions predominantly between 5 and 10 km below the surface have been inferred from m,•croearthquake seismograms [e.g., Sanford, 1983]. Evidence that the magma bodies are currently active includes (1) anomalously high earthquake activity (including swarms) in the Albuquerque to Socorro section of the rift, as compared to other parts of the rift [Sanford et al., 1979, 1981], (2) geomorphic and other geologic evidence for post-Pliocene activity in the Socorro area [Sanford et al., 1972; Chapin and Seager, 1975; Bachman and Mehnert, 1978; Ouchi, 1983-1, and (3) geodetic evidence for historic crustal deformation above the magma body [Reilinger and Oliver, 1976; Reilinger et al., 1980]. This paper reports and interprets new leveling measure-ments conducted in 1980 and 1981 by the National Geodetic Survey (NGS) in the Socorro area of the Rio Grande rift. The new observations confirm previously published results of crustal uplift apparently relate...
The U.S. Geological Survey conducted a 66-month-long study of earthquake activity near Albuquerque, New Mexico, during 1976-1981. Analysis of over 1000 hypocenters with magnitudes as large as 3.2 revealed that most of the seismicity fell into three regions: (1) the Socorro and Albuquerque areas of the Rio Grande rift, (2) the Mount Taylor area of the Jemez lineament, and (3) the Estancia basin. In the rift the hypocenters are shallow and largely confined to regions beneath the basins. Composite fault plane solutions suggest both normal and strike-slip faulting with an average T axis oriented WNW-ESE. Most of the young faults of the rift are seemingly inactive, and the rift as a whole cannot be delineated on the basis of seismicity. 11, 1975. Zoback, M. L., R. E. Anderson, and G. A. Thompson, Cainozoic evolution of the state of stress and style of tectonism of the Basin and Range province of the western United States, Philos. Trans. R.
Although geologic carbon sequestration projects have yet to induce or may never induce a damaging earthquake, experiences from other deep injection industries such as hydraulic fracturing, enhanced geothermal systems, and saltwater disposal suggest that effective quantitative seismic risk assessment is necessary for deep saline carbon capture and sequestration (CCS) projects. One such imminent CCS project is the San Juan Basin CarbonSAFE Phase III program. We utilize Monte Carlo probabilistic geomechanical analyses combined with observations of the geological and operational parameters of the San Juan Basin site and suggest that this project is of low induced seismic risk. The primary analysis is split into four sections. First, we assess the literature for faults and past seismicity, and at least five faulting scenarios are directly relevant. Second, we develop and calibrate an integrated earth model for the project site. Third, we perform Monte Carlo simulations that consider reasonable uncertainties of the geomechanical parameters. Of five tested faulting scenarios, only one presents high Coulomb failure functions, but fourth, we determine the risk to be low based on the combined lack of historical seismicity, the geological framework of the faulting scenario, and the presence of saltwater injection at the same depth as the proposed supercritical carbon dioxide injection. The most sensitive parameters in the geomechanical calculations are the fault dip and the coefficient of friction. The least sensitive are the fault strike and the orientation of the maximum horizontal principal stress.
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