The Oaxaca Earthquake of 30 September 1999 (Mw = 7.5): A Normal-faulting Event in the Subducted Cocos Plate

Singh, S. K.; Ordaz, Mario; Alcántara, L.; Shapiro, N. M.; Kostoglodov, V.; Pacheco, Jesús; Alcocer, Sergio M.; Gutiérrez, Carlos A. Mortera; Quaas, R.; Mikumo, Takeshi; Ovando, E.

doi:10.1785/gssrl.71.1.67

Cited by 51 publications

(24 citation statements)

References 20 publications

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“…Within this context, several researchers have put in evidence two main kind of seismogenic sources: interplate, thrust events, with epicentres located along the coast, depths ranging between Correspondence to: F. Leyton (fleyton@utalca.cl) 15 and 50 km (for a review, see Barrientos, 2007), and a second group of earthquakes located inside the subducting Nazca plate with continental epicentres of intermediate depth (greater than 50 km), known as intraplate or inslab events (Kausel and Campos, 1992;Barrientos, 2007). Similar classification has also been found in Mexico's subduction zone (Singh et al, 2000;García et al, 2005) and other subduction zones world-wide (for a review, see Astiz et al, 1988). Each one of these seismogenic sources have particular properties, producing a different effect on structures; hence, each one requires a special analysis (Saragoni et al, 2004;Astroza et al, 2002Astroza et al, , 2005Leyton et al, 2009b).…”

Section: Introductionmentioning

confidence: 77%

Preliminary re-evaluation of probabilistic seismic hazard assessment in Chile: from Arica to Taitao Peninsula

2009

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Abstract.Chile is one of the most seismically active countries in the world; indeed, having witnessed very large earthquakes associated with high horizontal peak ground accelerations, the use of probabilistic hazard assessment is an important tool in any decision-making. In the present study, we review all the available information to improve the estimation of the probabilistic seismic hazard caused by two main sources: shallow interplate, thrust earthquakes and intermediate depth, intraplate earthquakes. Using previously defined seismic zones, we compute Gutenberg-Richter laws and, along with appropriate attenuation laws, revaluate the probabilistic seismic hazard assessments in Chile. We obtain expected horizontal peak ground acceleration with a 10% of probability of being exceeded in 50 years, reaching from 0.6 g up 1.0 g in the coast and between 0.4 g and 0.6 g towards the Andes Mountains, with larger values in Northern part of the country. The present study improves our knowledge of geological hazards in Chile, enabling the mitigation of important human and material losses due to large earthquakes in the future.

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Section: Introductionmentioning

confidence: 77%

Preliminary re-evaluation of probabilistic seismic hazard assessment in Chile: from Arica to Taitao Peninsula

2009

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“…Open squares are in‐slab earthquakes [ Singh et al , 2000]; open circles are relocated earthquakes [ Pardo and Suarez , 1995]; solid triangles are seismic reflection data (Jalisco [ Michaud et al , 2000]); open triangle is from seismic refraction data (Oaxaca [ Nava et al , 1988]). Locations of megathrust main shocks (open diamonds) and their aftershocks (small circles) were given by Pacheco et al [1997] for Jalisco], Stolte et al [1986] for Michoacan, and Singh et al [2000] for Oaxaca. Bathymetry data were used to constrain the plate surface seaward of the trench [ Prol‐Ledesma et al , 1989; Pardo and Suarez , 1995].…”

Section: Thermal Modeling Of the Mexico Subduction Zonementioning

confidence: 99%

Thermal models of the Mexico subduction zone: Implications for the megathrust seismogenic zone

et al. 2002

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[1] It has been proposed that the seismogenic zone of subduction thrust faults is primarily controlled by temperature or rock composition changes. We have developed numerical models of the thermal structure of the Mexico subduction zone to examine the factors that affect the temperature of the subduction thrust fault. Although the oceanic plates subducting beneath Mexico are young, the top of the oceanic plate at the trench is cool, because of the lack of a thick cover of insulating sediments. Marine heat flow observations suggest that hydrothermal circulation may further cool the oceanic plate. This results in a cool subduction thrust fault, where the brittle part of the fault extends to depths of over 40 km. At these depths, even slight frictional heating may have significant effects on temperature along the thrust fault, particularly for regions with a high convergence rate and shallow plate dip. With the addition of a small amount of frictional heating, the temperatures of the deep (30-40 km) thrust fault are increased by over 200°C. As the observed downdip limit of rupture in recent well-constrained megathrust earthquakes is confined to depths above the intersection of the thrust fault and the continental Moho, a temperature of 350°C may control the downdip extent of the seismogenic zone. Thus, in order to be consistent with the observed shallow rupture areas, it is necessary to include a small amount of frictional heating, corresponding to an average shear stress of 15 MPa.INDEX TERMS: 3015 Marine Geology and Geophysics: Heat flow (benthic) and hydrothermal processes; 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 7230 Seismology: Seismicity and seismotectonics; 8130 Tectonophysics: Evolution of the Earth: Heat generation and transport; KEYWORDS: thermal models, subduction zone, megathrust earthquakes, seismogenic zone, heat flow, Mexico subduction zone Citation: Currie, C. A., R. D. Hyndman, K. Wang, and V. Kostoglodov, Thermal models of the Mexico subduction zone: Implications for the megathrust seismogenic zone,

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“…The location of the aftershocks, concentrated landward and down dip of the main shock, suggests a preference for the steeper dipping plane (Figure 1), but this is not definitive. For many tensional intermediate depth events in slabs, the steeper of the two nodal planes has been assumed to be the fault plane (e.g., the 1950 northern Chile event [ Kausel and Campos , 1992] or the 1999 Oaxaca, Mexico, earthquake [ Singh et al , 2000]). Yet, when a careful seismological analysis is conducted, for example, with aftershock relocations, results have varied.…”

Section: Introductionmentioning

confidence: 99%

“… Dmowska and Lovison [1992] found that moderate to large earthquakes at intermediate depth in slabs tend to concentrate near the down dip edge of the coupled plate interface where the locked plate boundary causes stress concentrations in adjacent regions. Examples of intraslab earthquakes that occur just below the down dip edge of a coupled plate interface include the 1931 ( M = 7.8) and 1999 ( M w = 7.5) Oaxaca, Mexico [ Singh et al , 2000; Mikumo et al , 2002]; the 1994 ( M w = 6.6) and 1997 ( M w = 7.3) Michoacan, Mexico [ Cocco et al , 1997; Mikumo et al , 1999]; the 1999 ( M w = 7) and 2000 ( M w = 6.5) Kodiak Island [ Ratchkovski and Hansen , 2001]; and the 1982 ( M w = 7.2) and 2001 ( M w = 7.7) El Salvador events. These dynamic models for intraplate events open the possibility that both the 1982 and 2001 tensional, intermediate depth El Salvador events are heralding the occurrence of a large underthrusting event in this region and identifying the moment release locations for this future earthquake.…”

Section: Introductionmentioning

confidence: 99%

The 13 January 2001 El Salvador earthquake: A multidata analysis

2003

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[1] On 13 January 2001, a large normal faulting intermediate depth event (M w = 7.7) occurred 40 km off the El Salvadorian coast (Central America). We analyze this earthquake using teleseismic, regional, and local data. We first build a kinematic source model by simultaneously inverting P and SH displacement waveforms and source time functions derived from surface waves using an empirical Green's function analysis. In an attempt to discriminate between the two nodal planes (30°trenchward dipping and 60°l andward dipping), we perform identical inversions using both possible fault planes. After relocating the hypocentral depth at 54 km, we retrieve the kinematic features of the rupture using a combination of the Neighborhood algorithm of Sambridge [1999] and the Simplex method allowing for variable rupture velocity and slip. We find updip rupture propagation yielding a centroid depth around 47 km for both assumed fault planes with a larger variance reduction obtained using the 60°landward dipping nodal plane. We test the two possible fault models using regional broadband data and near-field accelerograms provided by Universidad Centro Americana [2001]. Near-field data confirm that the steeper landward dipping nodal plane is preferred. Rupture propagated mostly updip and to the northwest, resulting in a main moment release zone of approximately 25 km Â 50 km with an average slip of $3.5 m. The large slip occurs near the interplate interface at a location where the slab steepens dip significantly. The occurrence of this event is wellexplained by bending of the subducting plate.

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The Oaxaca Earthquake of 30 September 1999 (Mw = 7.5): A Normal-faulting Event in the Subducted Cocos Plate

Abstract: Contributions were made (in alphabetical order) by J. A guirre 2, D. Almora 2, J. G.

Cited by 51 publications

References 20 publications

Preliminary re-evaluation of probabilistic seismic hazard assessment in Chile: from Arica to Taitao Peninsula

Preliminary re-evaluation of probabilistic seismic hazard assessment in Chile: from Arica to Taitao Peninsula

Thermal models of the Mexico subduction zone: Implications for the megathrust seismogenic zone

The 13 January 2001 El Salvador earthquake: A multidata analysis

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