Un reciente estudio, indica que algunos animales pueden sentir cambios químicos en el agua subterránea antes de que se produzca la ruptura sísmica.
La reciente publicación de Grant and Freund, et al., 2011 (Journal of Env. Res. and Public Health) da cuenta que en el 2009, días antes de la ocurrencia del sismo (6.3 Mw) de L'Aquila-Italia del mismo año, una colonia de sapos abandonó el estanque donde habitaban. Ellos sugieren que este tipo de comportamiento en los animales debería ser incorporado en lo que se denomina "Pronostico Sísmico" o "Pronostico de Terremotos"
En esta investigación se describe el mecanismo por el cual las rocas al estar sometidas a un alto nivel de esfuerzos/presión en el interior de la tierra (corteza terrestre), liberan partículas cargadas que reaccionan con el agua subterránea. El incremento en la emisión y/o liberación de partículas y posterior reacción química se daría dias antes de que se produzca la ruptura de las rocas (es decir el sismo). Los autores indican que los animales que viven en o cerca de ambientes con agua subterránea son altamente sensibles a cualquier cambio químico que se produzca en este medio, por lo tanto, el comportamiento de abandono/escape de los animales de este tipo de entornos marcaria una probable señal de cercania a la liberación abrupta de la energia sismica.
Pero este no es el unico caso, ya en anteriores oportunidades se observó que el comportamiento de algunos animales (anfibios, perros, pescados, aves...) se veía alterado antes de la ocurrencia de grandes sismos. Por ejemplo, en 1975 en Haicheng, China, muchas personas observaron que un gran número de serpientes comenzaban a salir de sus madrigueras un mes antes de que su ciudad fuera echada abajo por un fuerte sismo (7.3 Mw). Este caso es particular ya que este hecho se dio en época de invierno cuando dichos animales normalmente están hibernando. Su repentina salida podría considerarse un acto suicida ya que las temperatura están por debajo de cero, pero quizás la razón de su escape sea la misma del escenario de L'Aquila 2009.
Investigadores de la NASA han demostrado que cuando las rocas están sometidas a un alto nivel de esfuerzos, estas liberan particulas cargadas en forma de flujo, y este al alcanzar la superficie y entrar en contacto con el agua/aire reccionarían en un compuesto denominado Hidrogeno-Peroxido. No descartó que este flujo de particulas cargadas podría alcanzar niveles mas altos como la troposfera y/o ionosfera donde ya se ha registrado (con medidas GPS, magnetometría, otros) que se producen ciertas perturbaciones antes de la ocurrencia de grandes sismos.
jueves, 1 de diciembre de 2011
jueves, 24 de noviembre de 2011
Software: GeoMapApp useful geosciences mapping free software
GeoMapApp is an interactive portal displays whit a customized interface that allow showing earthquake epicentral locations Different parameters can be modified and animations saved saved in file .mov format. Created by the Marine Geoscience Data System group at Lamont-Doherty Earth Observatory of Columbia University. For more information about GeoMapApp see http://www.geomapapp.org
VIDEO: The 2010 Maule-Chile GREAT earthquake and its sequence of aftersocks
This video from Nathan Becker a specialist in tsunamis at the PTWC Hawaii, shows the seismic history of the great megathrust 2010 Maule earthquake, starting the January first. As it's known the 8.9 Mw mainshock occurred the February 27 and it was followed by a series of aftershocks with low to moderate magnitudes. Largest aftershock M=7.2 occurred the March 11. The animation shows the history during six months
miércoles, 26 de octubre de 2011
insights into the mysteries of materials and dynamics in the Earth's deep interior
domingo, 9 de octubre de 2011
Geodynamic and seismotectonic context of Peru
The subduction of the Nazca plate beneath South America constitutes the major tectonic characteristic in Peru. According to magnetic and geodetic data, the Nazca plate is continuously moving north-eastward (azimuth 78 degress )with an average velocity of 6 cm/yr (DeMets et al., 1990; Norabuena et al., 1999). This rapid convergence causes a high seismic coupling along the subduction interface giving raise to the occurrence of interplate and intraplate earthquakes with different magnitudes and depths. As a result of this process, different geomorphological structures and tectocni features have been created such as: the Peru-Chile trench, the Andean cordillera, the volcanic chain and fault systems. In case of the fault systems those are also sources of seismicity but of lower magnitudes. The figure shows all these features.
- The Peru-Chile trench: is a structure emplaced parallel to the Peruvian coast with a distance of about 160 km from the coast, bordering the contact between the Nazca plate and the South America plate.
- The Andean cordillera: the most obvious tectonic feature product of the continuous interaction of the Nazca plate, covers an area of 7,500 km, with heights of 6,000 m and higher. The volcanic chain is located in the southern part of Peru from 14º N to 25º S in Chile. Finally, fault systems are result of the deformation in the continental crust due to subduction process.
Different authors have proposed that the subduction zone could be divided into three zones according to its seismic activity (North, Central and South), this zones might be separated by two prominent geomorphologic features on the subduction plate: the Mendana fracture zone (10ºS) and the Nazca ridge (15ºS). The Nazca ridge location is considered as a barrier of rupture propagation as observed in the last Pisco earthquake (Mw8.0) in 2007 (Perfettini et al., 2010; Sladen et al., 2010). However, Okal et al. (2006), using tsunami simulations for the 1868 and 1687 events suggest that the Nazca ridge appears more like a hurdle than a barrier serving as a rupture barrier for certain events such as the 1604 event for the south and 1746 event to the north. Moreover, this feature is considered as a transition between a flat subduction zone to the north and a subduction steeply dipping to the south, with different azimuth of the shore line and seismicity activity (Okal et al., 2006; Sladen et al., 2010). The Mendana fracture zone is considered as a transition zone with a difference crustal age of about 10 Myr between north of the Mendana fracture zone and off the central and south of Peru (Muller et al., 1997).
- The volcanic chain: Located in the south of Peru from 14º S to 25º S in Chile. This chain is distributed along the Andean cordillera following an aparent linearity on NW-SE direction. Among the main volcanoes located in southern Peru: Coropuna (6425 m), Sabancaya (5795 m), Misti (5825 m), Ubinas (5672 m.), Chachani (3745 m.), Huaynaputina (4800 m.), Tutupaca (5806 m.), Yucamane (5508 m.). In northern and central Peru volcanic activity have disappeared approximately 8 Ma, due to changes in the form of the subduction process (Moroco 1980).
- The fault systems: are result of constant deformation process in the continental crust due to the subduction process. These faults are present in great number, from North to South along Sub-Andean zone and the eastern side of the Andes Mountains creating major folds in the contact with the Brazilian Shield. The main fault systems located in Peru are: Alto Mayo (AM), Satipo (SA), Madre de Dios (MD), in less proportion located on the high Cordillera and the Altiplano: the Cordillera Blanca (CB), Huaytapallana (HU), Tambomachay (TM). All fault systems owe their origin to a heterogeneous distribution of tensional and compressional efforts within thecontinent (James, 1978).
- The Andean cordillera: the most obvious tectonic feature product of the continuous interaction of the Nazca plate, covers an area of 7,500 km, with heights of 6,000 m and higher. The volcanic chain is located in the southern part of Peru from 14º N to 25º S in Chile. Finally, fault systems are result of the deformation in the continental crust due to subduction process.
Different authors have proposed that the subduction zone could be divided into three zones according to its seismic activity (North, Central and South), this zones might be separated by two prominent geomorphologic features on the subduction plate: the Mendana fracture zone (10ºS) and the Nazca ridge (15ºS). The Nazca ridge location is considered as a barrier of rupture propagation as observed in the last Pisco earthquake (Mw8.0) in 2007 (Perfettini et al., 2010; Sladen et al., 2010). However, Okal et al. (2006), using tsunami simulations for the 1868 and 1687 events suggest that the Nazca ridge appears more like a hurdle than a barrier serving as a rupture barrier for certain events such as the 1604 event for the south and 1746 event to the north. Moreover, this feature is considered as a transition between a flat subduction zone to the north and a subduction steeply dipping to the south, with different azimuth of the shore line and seismicity activity (Okal et al., 2006; Sladen et al., 2010). The Mendana fracture zone is considered as a transition zone with a difference crustal age of about 10 Myr between north of the Mendana fracture zone and off the central and south of Peru (Muller et al., 1997).
- The volcanic chain: Located in the south of Peru from 14º S to 25º S in Chile. This chain is distributed along the Andean cordillera following an aparent linearity on NW-SE direction. Among the main volcanoes located in southern Peru: Coropuna (6425 m), Sabancaya (5795 m), Misti (5825 m), Ubinas (5672 m.), Chachani (3745 m.), Huaynaputina (4800 m.), Tutupaca (5806 m.), Yucamane (5508 m.). In northern and central Peru volcanic activity have disappeared approximately 8 Ma, due to changes in the form of the subduction process (Moroco 1980).
- The fault systems: are result of constant deformation process in the continental crust due to the subduction process. These faults are present in great number, from North to South along Sub-Andean zone and the eastern side of the Andes Mountains creating major folds in the contact with the Brazilian Shield. The main fault systems located in Peru are: Alto Mayo (AM), Satipo (SA), Madre de Dios (MD), in less proportion located on the high Cordillera and the Altiplano: the Cordillera Blanca (CB), Huaytapallana (HU), Tambomachay (TM). All fault systems owe their origin to a heterogeneous distribution of tensional and compressional efforts within thecontinent (James, 1978).
viernes, 9 de septiembre de 2011
VIDEO: El gran terremoto de Tohoku: premonitores, sismo principal y réplicas
Si bien el sismo de Tohoku ocurrido el 11 de marzo de 2011alcanzó una gran magnitud 9.1Mw, este sismo fue precedido por un precursor de magnitud 7.2Mw el día 9 de Marzo. La animación posteada por Nathan B. (investigador del Pacific Tsunami Warning Center) muestra en 4 minutos (equivalentes al periodo de enero a Septiembre) la distribución espacio-temporal de los eventos premonitores, evento principal y réplicas de este gran sismo. Al observar la actividad sismica durante estos nueve meses se aprecia que durante los primeros meses la actividad sismica de fondo es normal o típica de la región, luego al producirse el evento premonitor le suceden el sismo principal y la serie de replicas que terminan por completar y estabilizar el área de ruptura del sismo. De este contexto se puede desprender que el evento premonitor del 9 de Marzo corresponde a lo que los autores que estudian el ciclo sismico denominan etapa de carga o fase pre-sismica, luego el sismo principal del 11 de Marzo corresponde a la etapa en la que se libera la energia sismica usualmente denominada fase co-sismica y finalmente la serie de réplicas que al parecer a la fecha aún no cesan corresponde a la etapa de relajación denominada fase post-sismica.
En el video cada segundo corresponde aproximadamente a 1 día, y la magnitud de los sismos se presenta en escala logaritmica.
domingo, 4 de septiembre de 2011
Debris avalanche simulation
This experiment has been done at IGP in Aug. 2011. The ingredients used were: Honey, fine sugar, sugar and little bit of patience... :-)
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