Earthquake Focal Mechanisms in the New Madrid Seismic Zone

Johnson, Greg A.; Horton, Steve; Withers, Mitch; Cox, Randy

doi:10.1785/0220130140

Cited by 19 publications

(27 citation statements)

References 31 publications

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“…This orientation is consistent with glacial isostatic adjustment [Calais et al, 2006] and the movement of the reference times series but appears incompatible with the more easterly orientation of maximum principal stress derived from earthquake focal mechanisms [Johnson et al, 2014].…”

Section: 1002/2015jb012049supporting

confidence: 58%

“…Fault geometry, extent of coseismic rupture, and slip in the 1811-1812 and 1450 events are assumed and detailed in section 5.1. Historic earthquakes on the Reelfoot and Cottonwood Grove faults are confined to be reverse and right lateral, respectively, which is consistent with present-day earthquake focal mechanisms [Johnson et al, 2014]. While some amount of oblique slip could have occurred during the 1811-1812 events, we do not have the information required to constrain these parameters.…”

Section: Postseismic Modelssupporting

confidence: 58%

“…Horizontal stresses are likely to be equal to or larger than vertical stresses at 5-10 km depth in order to explain the distribution of strike-slip and reverse faulting mechanisms [Johnson et al, 2014]. Therefore, at 10 km depth the normal stress on the Reelfoot fault will be at least the lithostatic stress minus the hydrostatic stress or roughly 165 MPa, which results in a value of (a À b)σ of 1.2 MPa.…”

Section: 1002/2015jb012049mentioning

confidence: 99%

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Crustal deformation in the New Madrid seismic zone and the role of postseismic processes

2015

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Global Navigation Satellite System data across the New Madrid seismic zone (NMSZ) in the central United States over the period from 2000 through 2014 are analyzed and modeled with several deformation mechanisms including the following: (1) creep on subsurface dislocations, (2) postseismic frictional afterslip and viscoelastic relaxation from the 1811–1812 and 1450 earthquakes in the NMSZ, and (3) regional strain. In agreement with previous studies, a dislocation creeping at about 4 mm/yr between 12 and 20 km depth along the downdip extension of the Reelfoot fault reproduces the observations well. We find that a dynamic model of postseismic frictional afterslip from the 1450 and February 1812 Reelfoot fault events can explain this creep. Kinematic and dynamic models involving the Cottonwood Grove fault provide minimal predictive power. This is likely due to the smaller size of the December 1811 event on the Cottonwood Grove fault and a distribution of stations better suited to constrain localized strain across the Reelfoot fault. Regional compressive strain across the NMSZ is found to be less than 3 × 10−9/yr. If much of the present‐day surface deformation results from afterslip, it is likely that many of the earthquakes we see today in the NMSZ are aftershocks from the 1811–1812 New Madrid earthquakes. Despite this conclusion, our results are consistent with observations and models of intraplate earthquake clustering. Given this and the recent paleoseismic history of the region, we suggest that seismic hazard is likely to remain significant.

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Section: 1002/2015jb012049supporting

confidence: 58%

Section: Postseismic Modelssupporting

confidence: 58%

Section: 1002/2015jb012049mentioning

confidence: 99%

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Crustal deformation in the New Madrid seismic zone and the role of postseismic processes

2015

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“…The seismic activity of the NMSZ is strongly associated with the intrusion of plutonic complexes (Hildenbrand and Hendricks, 1995). To explain the mechanism of intraplate earthquakes in the central United States, several studies based on the stress field in the NMSZ have been proposed (Sbar and Sykes, 1973;Sykes, 1978;Zoback and Zoback, 1981;Braile et al, 1982Braile et al, , 1984Gomberg, 1993;Gangopadhyay et al, 2004;Li et al, 2005;Johnson et al, 2014). Earthquakes within the embayment indicate a strikeslip fault system dominated by an approximate east-west compression due to asthenospheric viscous drag and/or ridge push (Zoback and Zoback, 1980).…”

Section: Geological and Tectonic Settingsmentioning

confidence: 99%

Relocation of Earthquakes in the New Madrid Seismic Zone: Estimation of 1D Velocity Structure and Geometry of a Seismogenic Fault

Park

Lee

Chiu

et al. 2015

Bulletin of the Seismological Society of America

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Determination of reliable hypocenters of earthquakes is crucial to earthquake seismology and to evaluate hazards associated with earthquakes. There are many associated computer codes for this purpose; however, most of the location algorithms are designed to determine hypocentral parameters based on previously determined velocity models. In contrast, we employed a location method that is independent of the initial velocity model, using a genetic algorithm (GA) to determine an optimal 1D velocity model and the locations of earthquakes. Using this GA, we relocated earthquakes that occurred in the New Madrid Seismic Zone (NMSZ) in the central United States between October 1989 and August 1992. The goal of this work was to delineate the possible fault planes by reliable relocation of those earthquakes and to determine a 1D velocity structure for the NMSZ. A total of 502 earthquakes recorded by 37 Portable Array for Numerical Data Acquisition (PANDA) stations were used in the relocation study. In the relocation process, the root mean square travel-time residuals were reduced by ∼35%, corresponding to an average of 2.3 km deeper in depth, 0.7 km shift in latitude, and 0.8 km shift in longitude compared with those in the initial catalog locations. The hypocenters of the earthquakes can be subdivided into four groups based on their spatial distributions. The group that corresponds to the Cottonwood Grove fault (CGF) in the southwestern NMSZ represents a very steep plane, whereas the other three groups fall into Reelfoot fault (RF). We inverted P-and S-wave travel times from the new hypocentral parameters to determine 1D velocity models. The resulting eightlayered velocity models consist of a 2 km thick surface layer followed by seven 2 km thick layers, with V P ranges from 5.36 to 6:74 km=s and V S ranges from 2.83 to 3:90 km=s for both CGF and RF regions.Online Material: Interactive visualizations of hypocentral distributions.

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“…Tradicionalmente, las soluciones de los mecanismos focales de los terremotos han sido una de las principales herramientas para el análisis sismotectónico de regiones continentales y zonas oceánicas, como lo muestran trabajos realizados en diferentes regiones del mundo: zonas de rift en el océano y el manto (Sykes, 1967;Isaacks and Molnar, 1969), Centroamerica y el Caribe Sykes, 1969, Lòpez, 2012), en el Medio Oriente (Nowroozi, 1972), la región de Azores-Alborán (Udías et al, 1976;Mezcua et al, 1991); en el Mediterraneo (Jackson and McKenzie, 1988), regiones continentales (Ekstrom and England, 1989), la región de Tayikistan (Sobolieva, 1990), el arco de islas Kuriles, Kamchatka y Aleutianas (Voronina et al, 1990), en Grecia Central (Papazachos and Kiratzi, 1992), el Mar Andaman (Guzmán-Speziale and Ni, 1993), el norte y el este de la falla Anatolia (Kiratzi, 1993), Japón (Kiratzi and Papazachos, 1996), las fosas tectónicas de América Central (Guzmán-Speziale, 2001), el arco volcánico de América Central relacionado con la subducción de la placa de Cocos (Guzmán-Speziale et al, 2005), Panamá (Camacho et al, 2010), en la zona de colisión del Arco de Panamá con la esquina del noroccidente de Suramérica (Vargas and Mann, 2013), Nuevo Madrid (Johnson et al, 2014), entre otros.…”

Section: Introductionunclassified

Caracterización Sismotectónica De La Región Del Valle Del Cauca Y Zonas Aledañas a Partir De Mecanismos Focales De Terremotos

Hurtado¹,

Pérez²

2016

Bol. Geol.

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Forma de citar:Salcedo, E., y Pérez J.L. 2016. Caracterización sismotectónica de la región del Valle del Cauca y zonas aledañas a partir de mecanismos focales de terremotos. Boletín de Geología, 38(3): 89-107. RESUMENEl presente trabajo analiza el mecanismo focal de 49 terremotos con magnitud Mw ≥ 4,8 en la región del Valle del Cauca y zonas aledañas, durante el periodo 1978-2010. Las soluciones fueron tomadas de los catálogos del Centro Internacional de Sismología (ISC, sigla en inglés) y del Centride Tensor de Momento Sísmico (GCMT, sigla en inglés). La profundidad de los eventos se distribuye entre superficiales e intermedios, hasta 215 km aproximadamente, asociados a la subducción de la placa Nazca, y unos pocos eventos superficiales que corresponden a la actividad de fuentes corticales en la placa continental Sudamericana. Concordante con el modelo de ambientes de regímenes de esfuerzos asociados con la deformación "estática" de la placa en subducción, se identifican cuatros ambientes sismotectónicos, que se distinguen por sus propias características sismológicas, tectónicas y régimen de esfuerzos. Se establece la tasa de deformación sismotectónica para cada uno de estos ambientes. El modelamiento del campo de esfuerzos de Coulomb muestra que el esfuerzo de cizalla crea una barrera que impide que el esfuerzo compresivo se proyecte al interior del continente en dirección SW-NE, interrumpiéndose en la zona en la fosa Colombo-Ecuatoriana. Mientras que el esfuerzo de tensión, aunque también es interrumpido, logra proyectarse al continente en dirección NW-SE, perpendicular al esfuerzo compresivo.Palabras claves: Sismotectónica, mecanismos focales, terremotos, campo de esfuerzos. SEISMOTECTONIC CHARACTERIZATION OF THE CAUCA VALLEY REGION AND SURROUNDING AREAS FROM THE EARTHQUAKE FOCAL MECHANISMS ABSTRACTThis paper analyzes the focal mechanism of 49 earthquakes with magnitude Mw ≥ 4.8 in the region of Valle del Cauca and surrounding areas during the period 1978-2010. The solutions were taken from the catalogs of the International Seismological Centre (ISC) and The Global Centroid-Moment-Tensor (GCMT) Project. The depth of the events is distributed between surface and intermediate about 215 km, associated with the subduction of the Nazca plate, and a few superficial events that correspond to the activity of cortical sources in the South American continental plate. In accord with model environments strong regimes associated with the "static" deformation of the subducting plate, four seismotectonic environments, are distinguished by its own seismic, tectonic and strong regime characteristics. The seismotectonic deformation rate is presented for each of these environments. The modeling of the Coulomb effort field shows that the shear creates a barrier that prevents the compressive effort is projected into the continent in SW-NE direction, interrupted in the Colombo-Ecuadorian trench. While the tensile effort, although is also interrupted, it manages to project the continent in NW-SE direction, perpendicular to compres...

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Earthquake Focal Mechanisms in the New Madrid Seismic Zone

Cited by 19 publications

References 31 publications

Crustal deformation in the New Madrid seismic zone and the role of postseismic processes

Crustal deformation in the New Madrid seismic zone and the role of postseismic processes

Relocation of Earthquakes in the New Madrid Seismic Zone: Estimation of 1D Velocity Structure and Geometry of a Seismogenic Fault

Caracterización Sismotectónica De La Región Del Valle Del Cauca Y Zonas Aledañas a Partir De Mecanismos Focales De Terremotos

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