Tectonic implications of the earthquake swarm of 1997 in the Michoacan Triangle, Mexico

Pacheco, J. F.; Valdés‐González, C.; Delgado, Hugo; Singh, S. K.; Zúñiga, F. Ramón; Mortera-Gutiérrez, C. A.; Santoyo, Miguel A.; Domı́nguez, Jaime; Barrón, Ricardo

doi:10.1016/s0895-9811(99)00040-1

Cited by 29 publications

(26 citation statements)

References 23 publications

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“…Focal mechanisms for the 1997 swarm showed considerable variation, ranging from left-lateral to right-lateral strike-slip as well as thrusting, also similar to the data presented here (Pacheco et al 1999). Based on evidence shown here, we believe that the swarm in May-July 2006 was caused by the movement of magma through the upper crust.…”

Section: Interpretation and Discussionsupporting

confidence: 85%

“…A previous swarm of earthquakes near Parícutin in 1997 was determined by Pacheco et al (1999) to also be aligned in a northeast-southwest direction similar to the 2006 swarm, with epicenters located within 10 km of those located in this study. Focal mechanisms for the 1997 swarm showed considerable variation, ranging from left-lateral to right-lateral strike-slip as well as thrusting, also similar to the data presented here (Pacheco et al 1999).…”

Section: Interpretation and Discussionsupporting

confidence: 64%

“…Tancitaro volcano, located approximately 10 km southwest of Parícutin, is one of the largest composite volcanoes in the MGVF, but has had no Holocene activity (Hasenaka 1994). The San Juanico-Buenavista fault is a northwest-southeast trending left-lateral oblique fault that passes roughly between the two volcanoes (Pacheco et al 1999).…”

Section: Geologic Settingmentioning

confidence: 99%

“…Swarms of earthquakes are not unknown in the region. In March 1997, a particularly vigorous swarm with 230 earthquakes, including five earthquakes exceeding local magnitude (M L ) 3.9, was located between Tancitaro and Parícutin (Pacheco et al 1999). Pacheco et al (1999) concluded that the activity was due to tectonic movement along a series of fractures in the area or along the San Juanico-Buenavista Fault itself.…”

Section: Geologic Settingmentioning

confidence: 99%

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Dike emplacement near Parícutin volcano, Mexico in 2006

2011

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A major seismic swarm occurred near Parícutin volcano between the end of May and early July 2006. More than 700 earthquakes with magnitude (M L ) exceeding 2.4 were located. Parícutin, located in the Michoacán-Guanajuato volcanic field in western Mexico, is well known as the site of the 1943 eruption in which a new 400 m cinder cone was constructed in what had been farmland. The 2006 swarm exhibits all of the characteristics typically associated with swarms of volcanic origins. The earthquake rate showed the typical ramp up and ramp down over the course of several days. Magnitudes were evenly distributed in time with a notably high b-value of 2.45. The earthquake locations cluster around a northeast-striking trend extending approximately 6 km. Over the first two weeks, hypocenters migrated steadily a few hundred meters per day, rising from 9 to 5 km depth and moving

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Section: Interpretation and Discussionsupporting

confidence: 85%

Section: Interpretation and Discussionsupporting

confidence: 64%

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

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Dike emplacement near Parícutin volcano, Mexico in 2006

2011

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“…In addition, the Tancítaro-Nueva Italia volcanic fi eld is located where the NW-SE-trending San Juanico-Buenavista strike-slip fault separates the Michoacán block from the Guerrero block ( Fig. 1; Johnson and Harrison, 1990;Pacheco et al, 1999). The NE-SW convergence of the North American and Cocos plates has caused a crustal anisotropy in the NE direction, along which numerous volcanic vents are aligned (Williams, 1950;Wilcox 1954;Hasenaka and Carmichael, 1985b;Connor, 1987).…”

Section: Tectonic and Geologic Settingmentioning

confidence: 99%

Origin of andesite in the deep crust and eruption rates in the Tancitaro-Nueva Italia region of the central Mexican arc

Ownby

Lange

Hall

et al. 2010

Geological Society of America Bulletin

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The Tancítaro-Nueva Italia region (~4400 km 2 ) is located within the west-central Mexican volcanic belt and spans ~80 km of arc length along the volcanic front. On the basis of 65 40 Ar/ 39 Ar ages, it is shown that a total volume of ~326 ± 57 km 3 of magma has erupted from >200 vents since 1.2 Ma. Nearly a third of this volume (103 ± 5 km 3 ) was erupted as crystal-rich andesite from a large stratovolcano, Volcán Tancítaro, whereas the remaining two-thirds (~223 ± 52 km 3 ) span the complete range from 51 to 63 wt% SiO 2 , are relatively crystal-poor, and were erupted from peripheral vents. The total proportions of erupted lava types are ~6%-7% basalt, ~18% basaltic andesite, and ~74%-76% andesite; there is no rhyolite and only a trace of dacite.There is no evidence that any signifi cant magma differentiation occurred in the upper crust along this arc segment. Based on phenocryst abundances and modes, majorand trace-element data, as well as phaseequilibrium experiments from the literature, the following mechanisms for formation of andesite in this region can be ruled out:(1) crystal fractionation of basalt/basaltic andesite in the upper crust, (2) magma mixing of basalt/basaltic andesite with dacite/ rhyolite, and (3) assimilation of granitoid by basalt/ basaltic andesite. Instead, the same body of evidence indicates that the andesites were formed primarily in the deep crust through partial melting (>20%) of hornblende-rich (~40%) gabbronorite. The basaltic andesites are required, owing to their elevated Ni concentrations, to be hybrids of the andesitic partial melts with basaltic residual liquids that have undergone variable two-pyroxene fractionation in the deep crust.

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