Nonuniform seismic slip rates along the Middle America Trench

McNally, Karen; Minster, J. B.

doi:10.1029/jb086ib06p04949

Cited by 113 publications

(42 citation statements)

References 30 publications

(20 reference statements)

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“…If the modern rate of SSEs has been constant since the last earthquake in 1950, the summed moment for all of the SSEs over this period (2 × 10 21 Nm) is nearly an order of magnitude higher than the moment released by the 2012 earthquake (3.5 × 10 20 Nm) and is equivalent to a M w 8.2 earthquake. SSEs thus appear to be releasing 80-90% of the slip associated with relative plate motion, consistent with the historically low seismic coupling coefficient for this margin (27)(28)(29). We suggest that Central America tends to have smaller earthquakes compared with many other subduction zones because a significant fraction of slip occurs via frequent SSEs.…”

Section: Resultsmentioning

confidence: 56%

Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture

Dixon

Jiang

Malservisi

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

124

167

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Significance Recent destructive megathrust earthquakes and tsunamis in Japan and Sumatra indicate the difficulty of forecasting these events. Geodetic monitoring of the offshore regions of the subduction zones where these events occur has been suggested as a useful tool, but its potential has never been conclusively demonstrated. Here we show that slow slip events, nondestructive events that release energy slowly over weeks or months, are important mechanisms for releasing seismic strain in subduction zones. Better monitoring of these events, especially those offshore, could allow estimates of the size of future earthquakes and their potential for damaging tsunamis. However, the predictive value of slow slip events remains unclear.

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Section: Resultsmentioning

confidence: 56%

Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture

Dixon

Jiang

Malservisi

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

124

167

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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.…”

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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“…0094-8276/86/006L-6080$03.00 569 in 1941 and 1973 (a 32 yr interval), and to the southeast, the Petatlan area in northern Guerrero had events in 1943 and 1979 (a 36 yr interval). An average recurrence interval for the plate boundary of 33 ± 8 yrs was found by McNally and Minster [ 1981 ), although different sub-segments have somewhat different intervals [Astiz and Kanamori, 1984 l. South of the Petatlan zone in the middle of the coast, the area void of recent large earthquake activity is the Guerrero seismic gap. The distance from Mexico City to the Guerrero gap is shorter than to any other region along the Mid-America trench.…”

Section: Introductionmentioning

confidence: 99%

“…Previous to the September 1985 earthquake, the Michoacan area, with its seismic quiescence and subducting fracture zone, was similar to the southern Oaxaca area, where the Tehuantepec Ridge is subducting, and where there are no large earthquakes in the historic record. One possibility suggested to explain the seismic quiescence in these areas was that features such as the Orozco fracture zone and the Tehuantepec Ridge may be locally affecting the subduction process, such that the area is subducting aseismically, or more slowly than adjacent regions of the plate boundary [Singh et al, 1980;McNally and Minster, 1981;Lefevre and McNally, 1985). Alterations of subdue- [Singh et al, 19851.…”

Section: Introductionmentioning

confidence: 99%

Tectonic Setting and Source Parameters of the September 19, 1985 Michoacan, Mexico Earthquake

Eissler¹,

Astiz²,

Kanamori³

1986

Geophysical Research Letters

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Abstract. Analysis of body waves and long-period surface waves from the September 1985 earthquake in coastal Michoacan, Mexico shows that the event was an interplate subduction event with a low dip angle fault plane (8=9°) striking parallel to the Mid-America trench (cp=288°) and a small component of left lateral motion (A.=72°) with a point source depth of 1 7 km, and a seismic moment in excess of 1 x 10 28 dyn cm. The earthquake was a multiple event, with a second source of identical moment, fault geometry, and depth occurring approximately 26 s after the first. Directivity in the body wave time function indicates that the second event occurred roughly 100 km to the southeast of the first. This suggests that the earthquake first broke the northern portion of the Michoacan gap, propagated with low moment release through the rupture zone of the 1981 Playa Azul earthquake, and then broke the remaining asperity in the southern section of the gap. The seismic moment determined from Rayleigh and Love waves is between 1.0 -1.7 x 10 28 dyn cm (Mw = 7 .9 -8.1 ), the largest moment determined to date for a Mexico subduction earthquake. Comparison of seismograms at Pasadena with records of other large Mexico events shows that the Michoacan earthquake is basically the same size as the 1932 Jalisco. Mexico earthquake, and clearly larger than other significant events in Mexico since 1932. The seismic moment and the time since the last large earthquake in Michoacan (in 1911) fit an empirical relation between moment and recurrence time found" for the Guerrero-Oaxaca region of the subduction zone. The large aftershock on September 21 (M 5 =7.5) has the same geometry as the mainshock, a somewhat larger source depth (22 km), a simple time function, and a seismic moment between 2.9 -4.7 x 10 27 dyn cm (Mw = 7.6 -7.7).

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Nonuniform seismic slip rates along the Middle America Trench

Cited by 113 publications

References 30 publications

Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture

Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture

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

Tectonic Setting and Source Parameters of the September 19, 1985 Michoacan, Mexico Earthquake

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