Recent measurements of crustal deformation related to the Socorro magma body, New Mexico
— Shawn Larsen and Robert Reilinger

Geophysical and geological observations indicate the existence of magma at intermediate depths in the crust beneath the Rio Grande rift in the vicinity of Socorro, New Mexico (Sanford and others, 1973, 1977; Brown and others, 1979). To a first approximation, the magma body apparently lies at a depth of 19 to 20 km and has the shape of a thin sill with a minimum areal extent of 1,700 km' (Rinehart and others, 1979). Evidence that the magma body is currently active includes: (1) anomalously high earthquake activity (including swarms) in the Al-buquerque to Socorro section of the rift, as compared to other parts of the rift (Sanford and others, 1979); (2) geomorphic and other geologic evidence for post-Pliocene activity in the Socorro area (Sanford and others, 1972; Chapin and Seager, 1975; Bachman and Mehnert, 1978); and (3) geodetic evidence for historic crustal deformation above the magma body (Reilinger and Oliver, 1976; Reilinger and others, 1980).

The purpose of this study is to use new releveling measurements performed by the National Geodetic Survey during 1980, along with previously reported releveling results, to better define modern defor-mation associated with the Socorro magma body. The new observations confirm previously published results of crustal uplift apparently related to magma migration in the middle crust and provide new insights on the spatial and temporal behavior of deformation in this section of the Rio Grande rift.