Constraints on Jalisco Block Motion and Tectonics of the Guadalajara Triple Junction from 1998–2001 Campaign GPS Data

Abstract

A GPS campaign network in the state of Jalisco was occupied for *36 h per station most years between 1995 and 2005; we use data from 1998-2001 to investigate tectonic motion and interseismic deformation in the Jalisco area with respect to the North America plate. The twelve stations used in this analysis provide coverage of the Jalisco Block and adjacent North America plate, and show a pattern of motion that implies some contribution to Jalisco Block boundary deformation from both tectonic motion and interseismic deformation due to the offshore 1995 earthquake. The consistent direction and magnitude of station motion on the Jalisco Block with respect to the North America reference frame, *2 mm/year to the southwest (95% confidence level), perhaps can be attributed to tectonic motion. However, some station velocities within and across the boundaries of the Jalisco Block are also non-zero (95% confidence level), and the overall pattern of station velocities indicates both viscoelastic response to the 1995 earthquake and partial coupling of the subduction interface (together termed ''interseismic deformation''). Our results show motion across the northern Colima rift, the eastern boundary of the Jalisco Block, which is likely to be sinistral oblique extension rather than pure extension. We constrain extension across both the Colima rift and the northeastern boundary of the Jalisco Block, the TepicZacoalco rift, to B8 mm/year (95% confidence level), slow compared to relative rates of motion at nearby plate boundaries.

Description of the Geology of the Tecolotlan Graben, Jalisco, Mexico

“…1). Currently, the rate of extension is ~5-6 mm/year for these larger grabens (Selvans et al, 2010). This pattern of early diffuse extension followed by more focused extension matches the predicted pattern of extensional deformation given by the numerical modeling work of Cowie (1998) and Cowie et al (2000).…”

“…Extension and associated sedimentation began in the Tecolotlan graben at ca. 5 Ma, approximately the same time as rifting and related volcanism began along the Colima Rift, which parallels the Tecolotlan graben to the east (Allan, 1986;Moore et al, 1994;Rosas-Elguera et al, 1996;Selvans et al, 2010). The lack of evidence for any modern fault activity in the graben suggests that the larger Colima and TepicZacoalco grabens are accommodating any regional extension that is still occurring, and that the smaller grabens, like the Tecolotlan graben, have become essentially inactive.…”

The A.D. 1567Mw 7.2 Ameca, Jalisco, Earthquake (Western Trans‐Mexican Volcanic Belt): Surface Rupture Parameters, Seismogeological Effects, and Macroseismic Intensities from Historical Sources

“…Active deformation within this array is dominantly extensional, with a north-northeast-south-southwest-oriented least principal stress (Suter, 1991;Ferrari and Rosas-Elguera, 2000). According to Ferrari and Rosas-Elguera (2000), the Pleistocene geologic slip rates are 0:1 mm=yr for the Amatlán de Cañas and San Marcos faults, whereas Global Positioning System geodetic measurements by Selvans et al (2011) indicate a current maximum extension rate of ≤ 8 mm=yr across the Ameca-San Marcos fault system. Crustal microseismicity was recorded by local networks in the Zacoalco region (Suárez et al, 1994;Pacheco et al, 1999) and in the region of the Amatlán de Cañas half-graben (Núñez-Cornú et al, 2002).…”

Crustal Architecture at the Collision Zone Between Rivera and North American Plates at the Jalisco Block: Tsujal Project

“…1). Selvans et al (2011) find also a slow motion of 2 mm/year to the southwest of the stations in the Jalisco Block relative to the NA Plate in a recent GPS campaign near the triple junction, which is compatible with such a tearing; however, motion could be related to the earthquake cycle behavior of subduction megathrusts and, therefore, the Jalisco Block might not have an independent motion.…”