Thermal structure, coupling and metamorphism in the Mexican subduction zone beneath Guerrero

Abstract

S U M M A R YTemperature is one of the most important factors that controls the extent and location of the seismogenic coupled and transition, partially coupled segments of the subduction interplate fault. The width of the coupled fault inferred from the continuous GPS observations for the steady interseismic period and the transient width of the last slow aseismic slip event (M w ∼ 7.5) that occurred in the Guerrero subduction zone in 2001-2002 extends up to 180-220 km from the trench. Previous thermal models do not consider this extremely wide coupled interface in Guerrero subduction zone that is characterized by shallow subhorizontal plate contact. In this study, a finite element model is applied to examine the temperature constraints on the width of the coupled area. The numerical scheme solves a system of 2-D Stokes equation and 2-D steady-state heat transfer equations.The updip limit of the coupling zone is taken between 100 and 150 • C, while the downdip limit is accepted at 450 • C as the transition from partial coupling to stable sliding. From the entire coupled zone, the seismogenic zone extends only up to ∼82 km from the trench (inferred from the rupture width of large subduction thrust earthquakes), corresponding to the 250 • C isotherm. Only a small amount of frictional heating is needed to fit the intersection of the 450 • C isotherm and the subducting plate surface at 180-205 km from the trench.The calculated geotherms in the subducting slab and the phase diagram for MORB are used to estimate the metamorphic sequences within the oceanic subducting crust. A certain correlation exists between the metamorphic sequences and the variation of the coupling along the interplate fault.

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

“…Song et al (2009) proposed that the USL represents a fluid-saturated portion of the oceanic crust, forming a high pore fluid pressure (HPFP) layer that is sealed by some low permeability layer, such as fine-grained blueschist, directly above it. Thermal modelling of the central Mexico subduction zone found a high pore pressure ratio of 0.98 along the subduction interface (Manea et al 2004), consistent with Song et al's (2009) HPFP layer. Kim et al (2010), on the other hand, proposed that the USL is highly heterogeneous upper crust that is composed of mechanically weak hydrous minerals (talc) that might be under high pore pressure.…”

Propagation of the 2001–2002 silent earthquake and interplate coupling in the Oaxaca subduction zone, Mexico

“…• C Curie isotherm is consistent with recent thermal models of the Guerrero subduction zone (Manea et al, 2004). The RP MAGSAT anomaly over Oaxaca subduction zone at the altitude of 350 km is induced by a constant magnetic field of 60,000 nT (Hinze et al, 1982).…”

“…For the sake of consistency we used the same densities: 3295 kg/m 3 for the upper mantle, 2700 and 2900 kg/m 3 for the upper part of the oceanic plate (basalt and gabbro), 3340 kg/m 3 for the oceanic lithosphere, 2670 kg/m 3 for the continental upper crust, and 3050 kg/m 3 for the continental lower crust. We also consider a depth for the transition from basalts to eclogites at ∼70 km, which is consistent with the recent thermal and metamorphic models for Guerrero (Manea et al, 2004). We used a density of 3300 kg/m 3 for eclogites.…”

Pattern of Temperature Structures in Himalayan Subduction Zone: A Review

“…So, the result suggests that there might have a great possibility to develop volcanic arc in the studied mantle wedge, where the temperature is 1420ºC. The maximum temperature in the mantle wedge which is achieved in the study is consistent with Tohoku subduction zone, 1400ºC in Northeast Japan (Honda 1985), Kamchatka subduction zone, 1450ºC in Mexico (Manea et al 2004).…”