Satellite remote sensing in earthquake prediction. A review

Sudden, violent movement of the earth's surface resulted of the release of energy into the atmosphere can destroy cities and claim lives. With the recent advances in space-borne data collecting methods which have made it possible monitoring the earth surface with different sensors, scientists are now able to better study the causes and signs of Earthquakes. Current researches are moving in the direction of pre-earthquake deformation detection. In order to make successful prediction all the related data must be collected from different space-borne sensors and ground-based stations. Past earthquakes should also be investigated for any phenomena that can occur before an earthquake. Surface deformation data are provided by GPS and SAR imaging, land surface temperature changes by ASTER, Landsat TM and ETM, different types of cloud studies using MODIS and Seawifs data, electromagnetic and ionosphere anomalies by ground passive stations and radon gas emissions in the faults areas by solid on the ground detectors. In this paper we tried to gather complete and helpful information of earthquake precursors which have been studied until now

Latent heat flux and air temperature anomalies along an active fault zone associated with recent Iran earthquakes

Pre-earthquake physical and chemical interactions in the earth’s ground may cause anomalies in latent heat flux, air and surface temperature. Earthquakes occur when the energy accumulated in rocks releases. Sometimes, the movements of the ground cause ruptures in the earth’s surface and sometimes the two sides of an existing fault shift towards each other. In a structurally complex and inhomogeneous collision region such as the Iranian Plateau, seismicity is not the result of activity of a single fault but is due to energy discharge in fault zones hundreds of kilometers wide. Changes in latent heat flux and temperature, on and above the earth’s surface can be detected with thermal infrared (TIR) sensors such as NOAA-AVHRR, Terra/Aqua-MODIS, etc. Spatio-temporal distributions of surface latent heat flux (SLHF) and air temperature before and after two recent earthquakes in Iran have been studied. Anomalous patterns of higher SLHF formed a few days before the earthquakes of 20 Dec 2010 (6M) and 27 Jan 2011(6.5M) occurred in Kerman province and disappeared after the main events. Data analyses revealed at least 2–4 °C rises in air temperature along the nearby fault zone, as well. These changes were also in accordance with the abnormal relative humidity over the region. Significant rises in SLHF and air temperature may lead us to understand the energy exchange mechanism during the earthquakes. These anomalies prior to impending earthquakes can be attributed to the thermodynamic, degassing and ionization processes which are believed to be activated by the accumulated stress in the ground, insensible movements of the tectonic blocks, and micro-fracturing in the rocks especially along area’s active faults. Continuous monitoring of these potential precursors helps in differentiating earthquake related variations from seasonal changes and atmospheric effects

Detection of precursory signals of past earthquakes using integration of spatio-temporal parameters

The preparation process of an impending earthquake may leave fingerprints on the earth’s surface. Earthquakes are triggered when the energy accumulated in rocks releases causing ruptures in the ground or movements in place of the existing faults. Elastic strain in rocks, formation of micro-cracks, gas releases and other chemical or physical activities in the earth’s crust before and during earthquakes has been reported to cause rises in temperature, surface latent heat flux (SLHF), upwelling index and chlorophyll-a (Chl-a) concentration on the ground or sea surface. This study examines variations of the mentioned factors before several past oceanic, coastal earthquakes occurred at the Pacific and Indian Oceans together with two pairs of successive inland earthquakes in Kerman and Azerbaijan provinces, Iran. The sudden partial releases of the elastic energy which has resulted to the main events are believed to be detected by seismographs and remote sensing techniques. Pre-earthquake anomalies prior to all case study earthquakes were detected. Our detailed analyses on oceanic/coastal earthquakes revealed 1–5°C rises in surface temperature in epicenter areas. Considerable anomalies in Chl-a concentration, five weeks to a day before the earthquake events which are accompanied by the raises in upwelling indices were detected. Time series of SLHF also showed meaningful rises from one month to one week before the main events. The anomalous patterns started developing several weeks before earthquakes and disappeared after the main shocks. Significant rises in SLHF may lead us to understand the energy exchange mechanism during earthquakes and at the period of aftershocks, as well. The most interesting factor which yielded considerable results for almost all earthquake instances was SLHF. In case of offshore and coastal earthquakes the Chl-a was found to be the most common precursor. Most of the anomalous patterns were in accordance with local and regional active faults which have been already proposed as triggering structures by international research organizations. The seismographic records were also successfully used for confirmation of the earth’s movements during the preparation stage of the main event of Ahar as an underlying cause for remotely sensible phenomena. The author strongly believes that with proper use of remote sensing data, expert analysis of seismographs from nearby stations (which unfortunately are not existing everywhere), advanced in-situ measurement devices, and thorough information about local and regional active faults developing local earthquake prediction systems for earthquake prone region would not be impossible