Terremotos

Hace rato que no actualizaba este blog, pero sin lugar a dudas, el terremoto recién pasado en Chile hace necesario esto, ya que hay varios temas dando vuelta en internet, que han adquirido el nivel de mitos en varios foros que he visitado en estos días, particularmente lo del el cambio en el eje terrestre o las predicciones acerca del terremoto.

Bueno, lo primero es lo primero: acerca de las predicciones.

He leído algunas predicciones, como la del "Mago Yin" y teorías dosmildoceanas que para el publico común son muy atractivas de creer.

Así también, a las horas del terremoto salio un articulo en terra en el que se aseguraba que u estudio realizado por expertos lo habría anticipado.

Vamos por parte.

Lo del supuesto mago no me lo creo para nada y ni siquiera lo voy a analizar, sin embargo, la respuesta o la información entregada por el sismólogo consultado en la misma noticia a mi parecer es deficiente, ya que el estudio ya se encontraba publicado (es más, se había enviado a revisión en Marzo del 2007.

El articulo en si (publicado en Physics of the Earth & Planetary Interiors, Vol. 175, issues 1-2, pp. 78-85) concluye que la parte sur del gap Concepción-Constitución ha acumulado un déficit de deslizamiento que es más que suficiente para producir un gran terremoto de magnitud 8.0-8.5, aproximadamente. Esto es, por supuesto, el peor escenario y es necesario que sea refinado en trabajos adicionales.

Pero el articulo no menciona una fecha exacta, un año o un mes, por lo que el titulo de la noticia de terra es un tanto alarmista.

El articulo completo se encuentra acá: download (pdf, sin compresión ni contraseña)

Por otro lado, tenemos lo del cambio en el angulo de rotación de la tierra a partir del terremoto de Chile. Esto es totalmente cierto, me declaraba ignorante en el tema, pero si, se han registrado modificaciones al eje terrestre con varios terremotos, Chile 2010, Indonesia 2004, Chile 1960, etc., claro que son cambios prácticamente imperceptibles y solo demostrables a partir de modelos computacionales. La explicación de este fenómeno es simple, tal desplazamiento de masa en la zona de subducción tiene una respuesta a nivel planetario. La tierra, luego del terremoto trata de volver al equilibrio, y como hace esto, modificando el eje terrestre con respecto a la nueva distribución de masa, es lo que los expertos denominan efecto "ice-skater".

Mas información acerca de los efectos del terremoto de Chile la encontraran en el siguiente enlace.

Y finalmente, les traigo libros relacionados con el tema:

Earthquakes: Plate Tectonics and Earthquake Hazards

By Timothy, Ph.D. Kusky

Description:

Every day parts of the surface of the Earth are rattled by earthquake tremors, and occasionally, some regions are shaken violently during earthquakes, resulting in widespread damage and destruction. Earthquakes in Iran, Turkey, and Japan have demonstrated how the motion of the Earth's tectonic plates can suddenly make apparently safe environments dangerous and even deadly."Earthquakes" focuses on the furious power of nature unleashed and the massive devastation that is often a result of the relentless forces that build up within the Earth. Presenting the main ideas of plate tectonics, this comprehensive and insightful reference provides readers with an understanding of how, why, and where most earthquakes occur. Coverage includes what happens during an earthquake, using many examples of hazards such as landslides, passage of seismic-earthquake waves through the ground, and other phenomena that people have encountered during real earthquakes. Black-and-white photographs and line illustrations, an index, a glossary, and a geologic timescale enhance this in-depth resource.Chapters include: General Earth Structure and Plate Tectonics; Divergent Plate Boundaries; Transform Plate Boundaries and Transform Faults; Convergent Margins; Earthquakes; Earthquake Hazards; Earthquake Prediction, Preparation, and Response; and, Descriptions of Earthquake Disasters.

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Earthquake Early Warning Systems

By Paolo Gasparini, Gaetano Manfredi, Jochen Zschau

Description:

During the past few decades, economic losses and human casualties due to natural disasters increased exponentially on our planet, mainly because of the increased density of population and industry in high hazard areas. Although the prediction of earthquakes is not practicable yet, the present technology allows a prompt identification of the onset of any dangerous seismic event before it hits an urban area. Earthquake early warning can provide an alert within a few tens of seconds in advance. This small lead time may be used to minimize property damage and loss of lives in metropolitan areas and to aid emergency response. The book provides information on the major EEW systems in operation and on the state of the art of the different blocks forming an EW system: the rapid detection and estimation of the earthquake s focal parameters, the signal transmission, the engineering interface and the information reliability/false alarm problem.

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Fault-Zone Properties and Earthquake Rupture Dynamics

By Eiichi Fukuyama

Description:

The dynamics of the earthquake rupture process are closely related to fault zone properties which the authors have intensively investigated by various observations in the field as well as by laboratory experiments. These include geological investigation of the active and fossil faults, physical and chemical features obtained by the laboratory experiments, as well as the seismological estimation from seismic waveforms. Earthquake dynamic rupture can now be modeled using numerical simulations on the basis of field and laboratory observations, which should be very useful for understanding earthquake rupture dynamics.

Features:

* First overview of new and improved techniques in the study of earthquake faulting

* Broad coverage

* Full color

Benefits:

* A must-have for all geophysicists who work on earthquake dynamics

* Single resource for all aspects of earthquake dynamics (from lab measurements to seismological observations to numerical modelling)

* Bridges the disciplines of seismology, structural geology and rock mechanics

* Helps readers to understand and interpret graphs and maps

Also has potential use as a supplementary resource for upper division and graduate geophysics courses.

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