Fault kinematics in northern Central America and coupling along the subduction interface of the Cocos Plate, from GPS data in Chiapas (Mexico), Guatemala and El Salvador

Aurore Franco (1) , Cécile Lasserre (2) , H. Lyon-Caen (1) , Vladimir Kostoglodov (3) , E. Molina (4) , M. Guzman-Speziale (5) , D. Monterosso (6) , V. Robles (7) , C. Figueroa (8) , W. Amaya (9) , Eric Barrier (10) , L. Chiquin (11) , S. Moran (11) , Olivier Flores (12) , J. Romero (13) , J.A. Santiago (14) , M. Manea (14) , V.C. Manea (14)

1 LGENS - Laboratoire de géologie de l'ENS
2 ISTerre - Institut des Sciences de la Terre
3 Instituto de Geofísica
4 Instituto Nacional de Sismologıa, Vulcanologıa, Meterologıa e Hidrologia
5 Centro de Geosciencias
6 6Coordinadora Nacional para la Reduccion de Desastres
7 IGN - Instituto Geografico Nacional
8 Instituto Geografico y Catastro Nacional
9 Instituto Geografico y Catastro Nacional
10 EMBS - Evolution et Modélisation des Bassins Sédimentaires
11 Centro Universitario del Norte
12 Centro de Estudios Superiores de Energia y Minas
13 Geologia Ambiental e Economia
14 Instituto de Geofisica [Mexico]

New GPS measurements in Chiapas (Mexico), Guatemala and El Salvador are used to constrain the fault kinematics in the North America (NA), Caribbean (CA) and Cocos (CO) plates triple junction area. The regional GPS velocity field is first analysed in terms of strain partitioning across the major volcano-tectonic structures, using elastic half-space modelling, then inverted through a block model. We show the dominant role of the Motagua Fault with respect to the Polochic Fault in the accommodation of the present-day deformation associated with the NA and CA relative motion. The NA/CA motion decreases from 18-22 mm yr−1 in eastern Guatemala to 14-20 mm yr−1 in central Guatemala (assuming a uniform locking depth of 14-28 km), down to a few millimetres per year in western Guatemala. As a consequence, the western tip of the CA Plate deforms internally, with ≃9 mm yr−1 of east-west extension (≃5 mm yr−1 across the Guatemala city graben alone). Up to 15 mm yr−1 of dextral motion can be accommodated across the volcanic arc in El Salvador and southeastern Guatemala. The arc seems to mark the northern boundary of an independent forearc sliver (AR), pinned to the NA plate. The inversion of the velocity field shows that a four-block (NA, CA, CO and AR) model, that combines relative block rotations with elastic deformation at the block boundaries, can account for most of the GPS observations and constrain the overall kinematics of the active structures. This regional modelling also evidences lateral variations of coupling at the CO subduction interface, with a fairly high-coupling (≃0.6) offshore Chiapas and low-coupling (≃0.25) offshore Guatemala and El Salvador.

Mots clés: Kinematics of crustal and mantle deformation; Dynamics and mechanics of faulting; Seismic cycle; Plate motions; Subduction zone processes; Satellite geodesy

Domaines: Sciences de la Terre

Aurore Franco, Cécile Lasserre, H. Lyon-Caen, Vladimir Kostoglodov, E. Molina, et al.. Fault kinematics in northern Central America and coupling along the subduction interface of the Cocos Plate, from GPS data in Chiapas (Mexico), Guatemala and El Salvador. Geophysical Journal International, 2012, 189 (3), pp.1223-1236. ⟨10.1111/j.1365-246X.2012.05390.x⟩. ⟨hal-00764116⟩