Crustal velocity field of Mexico from continuous GPS measurements, 1993 to June 2001: Implications for the neotectonics of Mexico

Abstract

We combine velocities for 14 continuous GPS stations spanning Mexico and 173 additional continuous GPS sites on the North American and Pacific plates to study the large‐scale deformation of Mexico. The new station velocities, which are derived from more than 6000 days of previously unused GPS data, provide the first ever view of the crustal velocity field of Mexico. Key results are as follows: (1) Areas north of the Mexican Volcanic Belt, not including Baja California, move with the North American plate interior within the 1–2 mm yr−1 station velocity uncertainties. Station velocities for the Mexican Basin and Range are consistent with no present‐day extension and yield an upper 95% limit of 1–3 mm yr−1 for any regional extension. (2) South of the Mexican Volcanic Belt, five of the six sites move significantly relative to the North American plate. All sites in the Yucatan Peninsula move toward the east at 3–4 mm yr−1, possibly defining an independent Yucatan block. (3) Site velocities are consistent with limits of 0–4 mm yr−1 for present slip across the Mexican Volcanic Belt. (4) Tampico, on the gulf coast, exhibits eastward motion consistent with gravity sliding known to occur in the adjacent Mexican Ridges fold belt. (5) Southeastward motion of La Paz relative to the Pacific plate is consistent with the hypothesis that the Baja Peninsula is not fully attached to the Pacific plate. (6) Residual velocities for 160 North American plate GPS stations outside of Mexico exhibit no coherent regional patterns indicative of internal plate deformation.