The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks

Singh, S. K.; Havskov, Jens; McNally, Karen; Ponce, Lisandro Cruz; Hearn, Thomas M.; Vassiliou, M. S.

doi:10.1126/science.207.4436.1211

Cited by 51 publications

(22 citation statements)

References 10 publications

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“…The Oaxaca profile passes through the rupture area of the 1978 M W 7.6 earthquake (Figure 7d). The 1‐month aftershocks for this earthquake extend from 20 to 100 km from the trench [ Singh et al , 1980; Stewart et al , 1981]. As the aftershocks were located relative to the main shock, the relative positions of each earthquake are very well constrained.…”

Section: Mexico Seismogenic 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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Section: Mexico Seismogenic Zonementioning

confidence: 99%

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

et al. 2002

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“…The main shock was located at 15.77°N, 96.80°W McNally and Minster, 1981] at a depth of 18 km [Stewart et al, 1981]. Local seismic observations with portable field seismographs showed that the aftershocks were distributed over an area of $80 km (in the E-W direction) Â 65 km (in the N-S direction) and that their hypocenters had increasing depths inland from the trench [Singh et al, 1980], as shown in Figure 2. The fault plane solution has been obtained from P wave first motions at the World-Wide Standardized Seismograph Network (WWSSN) and Mexican stations, yielding two nodal planes (d = 14°, f = 270°and d = 79°, f = 127° [Stewart et al, 1981]), and the northward dipping nodal plane at $14°has been taken as the fault plane to be consistent with the depth distribution of aftershocks.…”

Section: Rupture Processes Of the 1978 And 1999 Oaxaca Earthquakesmentioning

confidence: 99%

Coseismic and postseismic stress changes in a subducting plate: Possible stress interactions between large interplate thrust and intraplate normal‐faulting earthquakes

et al. 2002

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A large intraplate, normal‐faulting earthquake (Mw = 7.5) occurred in 1999 in the subducting Cocos plate below the downdip edge of the ruptured thrust fault of the 1978 Oaxaca, Mexico, earthquake (Mw = 7.8). This situation is similar to the previous case of the 1997 normal‐faulting event (Mw = 7.1) that occurred beneath the rupture area of the 1985 Michoacan, Mexico, earthquake (Mw = 8.1). We investigate the possibility of any stress interactions between the preceding 1978 thrust and the following 1999 normal‐faulting earthquakes. For this purpose, we estimate the temporal change of the stress state in the subducting Cocos plate by calculating the slip distribution during the 1978 earthquake through teleseismic waveform inversion, the dynamic rupture process, and the resultant coseismic stress change, together with the postseismic stress variations due to plate convergence and the viscoelastic relaxation process. To do this, we calculate the coseismic and postseismic changes of all stress components in a three‐dimensional space, incorporating the subducting slab, the overlying crust and uppermost mantle, and the asthenosphere. For the coseismic stress change we solve elastodynamic equations, incorporating the kinematic fault slip as an observational constraint under appropriate boundary conditions. To estimate postseismic stress accumulations due to plate convergence, a virtual backward slip is imposed to lock the main thrust zone. The effects of viscoelastic stress relaxations of the coseismic change and the back slip are also included. The maximum coseismic increase in the shear stress and the Coulomb failure stress below the downdip edge of the 1978 thrust fault is estimated to be in the range between 0.5 and 1.5 MPa, and the 1999 normal‐faulting earthquake was found to take place in this zone of stress increase. The postseismic variations during the 21 years after the 1978 event modify the magnitude and patterns of the coseismic stress change to some extent but are not large enough to overcome the coseismic change. These results suggest that the coseismic stress increase due to the 1978 thrust earthquake may have enhanced the chance of occurrence of the 1999 normal‐faulting event in the subducting plate. If this is the case, one of the possible mechanisms could be static fatigue of rock materials around preexisting weak planes involved in the subducting plate, and it is speculated that that one of these planes might have been reactivated and fractured because of stress corrosion cracking under the applied stress there for 21 years.

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“…In the Oaxaca region many studies such as microearthquake observation campaigns, aftershocks studies (for the 1978, 1980, 1982, and 1995 earthquakes), and refraction seismic studies among others have been carried out (e.o~, Ponce et al, 1979;Ntifiez-Cornfi et al, 1979;Singh et al, 1980;Chael and Stewart, 1982;Jimdnez et al, 1983;Astiz and Kanamori, 1984;Yamamoto et al, 1984;Nava, 1984;Ndfiez-Cornfi and Ponce, 1984;Quintanar, 1985;Nava et aL, 1987;Ntifiez-Corntl, 1987;Ntifiez-Corntl and Ponce, 1989;Nfifiez-Cornfi et al, 1993). Thus, the Oaxaca Region is probably the best-studied zone in Mexico from the seismic point of view.…”

Section: Introductionmentioning

confidence: 99%

A Double Seismic Front and Earthquake Cycles Along the Coast of Oaxaca, Mexico

Núñez-Cornũ

1996

Seismological Research Letters

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The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks

Cited by 51 publications

References 10 publications

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

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

Coseismic and postseismic stress changes in a subducting plate: Possible stress interactions between large interplate thrust and intraplate normal‐faulting earthquakes

A Double Seismic Front and Earthquake Cycles Along the Coast of Oaxaca, Mexico

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