Recent Vertical Crustal Movements from Leveling Observations in the Rio Grande Rift: A Review

摘要

Analysis of repeated leveling surveys suggests significant contemporary vertical deformation in at least three distinct areas in the vicinity of the Rio Grande rift. These areas include Socorro, New Mexico; the Diablo Plateau region of Trans-Pecos Texas; and the Espanola basin in northern New Mexico. The Socorro area is characterized by uplift relative to its surroundings. Maximum relative uplift of about 20 cm between 1911 and 1951 occurred about 25 km north of Socorro, corresponding to an average relative velocity of 5 mm/yr. The primary anomaly, defined by a north-south profile between El Paso, Texas, and Albuquerque, New Mexico, extends from 15 km south to 70 km north of Socorro. The Diablo Plateau region is also characterized by relative uplift. Uplift of approximately 13 cm during the period from 1934 to 1958 was observed along an approximately east-west profile from El Paso, Texas, to Carlsbad, New Mexico. The leveling anomaly suggests broad uparching of the basin and range structures between El Paso and Carlsbad, with the maximum occurring near the eastern side of the Diablo Plateau. In contrast to the observed relative uplift near Socorro and on the Diablo Plateau, leveling data within the Espanola basin in northern New Mexico show a pronounced zone of relative subsidence. Maximum observed subsidence relative to nearby benchmarks was 4.9 cm between September 1934 and March 1939. Subsidence is observed over a distance of approximately 19 km, extending from 4 km north to 23 km north-northwest of Espanola. The consistency of the available geological and geophysical evidence suggests that these three leveling anomalies are due to crustal deformation and not to measurement errors or near surface effects. Deformation in all three areas can be related, with different degrees of uncertainty, to crustal magmatic activity. (ERA citation 04:028177)