Overview of Recent Coastal Tectonic Deformation in the Mexican Subduction Zone

Abstract

Holocene and Pleistocene tectonic deformation of the coast in the Mexico subudction margin is recorded by geomorphic and stratigraphic markers. We document the spatial and temporal variability of active deformation on the coastal Mexican subduction margin. Pleistocene uplift rates are estimated using wave-cut platforms at ca. 0.7-0.9 m/ka on the Jalisco block coast, Rivera-North America tectonic plate boundary. We examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the Holocene up to ca. 3 ± 0.5 m/ka. In contrast, steady rates of uplift (ca. 0.5-1.0 m/ka) in the Pleistocene and Holocene characterize the Michoacan coastal sector, south of El Gordo graben and north of the Orozco Fracture Zone (OFZ), incorporated within the Cocos-North America plate boundary. Significantly higher rates of surface uplift (ca. 7 m/ka) across the OFZ subduction may reflect the roughness of subducting plate. Absence of preserved marine terraces on the coastal sector across El Gordo graben likely reflects slow uplift or coastal subsidence. Stratigraphic markers and their radiocarbon ages show late Holocene (ca. last 6 ka BP) coastal subsidence on the Guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence. Temporal and spatial variability in recent deformation rates on the Mexican Pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction, such as crustal faults, subduction erosion and underplating of subducted materials under the southern Mexico continental margin.

Rupture Process During the Mw 8.1 2017 Chiapas Mexico Earthquake: Shallow Intraplate Normal Faulting by Slab Bending

“…Southern Mexico is a seismically active region, where the Cocos and Rivera plates are subducting northeastward beneath the North America plate at a rate of ~60 mm/yr and ~20 mm/yr, respectively (DeMets et al, 2010), and where the large earthquakes (M > 7) have struck at short time intervals during the past century (e.g., Pardo & Suarez, 1995;Ramírez-Herrera et al, 2011;Singh et al, 1981). The southern Mexico subduction zone (Figure 1) is noted for the frequent occurrence of the large intraplate, normal-faulting earthquakes at shallow and intermediate depths within the subducting Cocos plate (e.g., Mikumo et al, 2002;Rebollar et al, 1999b;Santoya et al, 2005;Singh et al, 1985), which can be explained by stress transfer from the preceding interplate earthquakes (Lemoine et al, 2002;Mikumo et al, 1999Mikumo et al, , 2000 and by slab unbending due to continental loading (Fujita & Kanamori, 1981).…”

“…The Servicio Sismológico Nacional of the Universidad Nacional Autónoma de México (SSN UNAM) reported that the earthquake occurred offshore of the town on Pijijiapan, with a hypocenter 58 km beneath 14.85°N, 94.11°W ( Figure 1). The SSN assigned it a moment magnitude of M W 8.2, making it one of the largest instrumentally recorded earthquakes in Mexico (Ramírez-Herrera et al, 2011;Singh et al, 1981;SSN UNAM Special Report, 2017). A cross section of the source area is shown in Figure 2a, summarizing the focal depths of the centroid moment tensor (CMT) solutions fetched from database of the Japan Meteorological Agency (JMA; http://www.data.jma.go.jp/svd/eqev/data/mech/world_cmt/fig/cmt20170908044921.html), the Intraplate normal faulting in a subducting plate can occur in a tensile stress field due to plate bending at shallow depths and near the trench, to slab pull from the negative buoyancy of the subducting plate, and to unbending of the subducting plate beneath a strongly coupled interface at intermediate depths beneath the continental plate (Astiz et al, 1988;Fujita & Kanamori, 1981;Isacks et al, 1968;Spence, 1986).…”

Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

“…Regional subsidence of an active margin is generally related to tectonic erosion, and therefore, such long-term subduction erosion regimen for the Manzanillo area implies trench retreat along the margin (MERCIER DE LEPINAY et al 1997). Recent overview of RAMÍREZ-HERRERA et al (2011) confirm that, although spatial and temporal variability exists, coastal subsidence is occurring at the southern Colima Graben and the Guerrero seismic gap near Acapulco, whereas coastal uplift is occurring between Puerto Vallarta and Manzanillo and along the coast south of the Colima/El Gordo Graben until Lazaro Cardenas, located southeast of Acapulco.…”

Mapping and historical reconstruction of the great Mexican 22 June 1932 tsunami

“…The incorporation of historical research techniques into the natural hazards studies has proven to be a useful tool, as there are many types of data sources that can be included: paintings, photographs, prints, legends, letters, government reports, etc. (Wang and Zhang, 1988;Pfister, 1999;Naulet et al, 2001;Wagner and Suda, 2004). These sources of information can be subjective, but the subjectivity can be resolved through critical evaluation of the information (Pfister, 1999).…”

“…(Wang and Zhang, 1988;Pfister, 1999;Naulet et al, 2001;Wagner and Suda, 2004). These sources of information can be subjective, but the subjectivity can be resolved through critical evaluation of the information (Pfister, 1999).…”