Geology, tectonics and topography underlined by L'Aquila earthquake TIR precursors

Abstract

Anomalous thermal infrared (TIR) emissions have widely been detected by satellite sensors before the major earthquakes. A recent processing technique for geostationary thermal data, developed for the case of the 2009 April 6, magnitude 6.3 L'Aquila earthquake, makes it possible to identify areas of enhanced TIR emissions around the epicentral region at a mean distance of less than 50 km but inside a radius of about 100 km. The index, called Night Thermal Gradient (NTG), derived from 4-D time-series data (two spatial and two temporal coordinates), identifies TIR anomalies by following the temperature trend during night, when the surface of the Earth is expected to cool. Leading up to the L'Aquila earthquake, an anomalous warming trend was observed. In this study, the anomalous NTG pattern is compared to the expected normal trend, taking into account the seismogenic faults, the overall tectonic setting, lithological spatial features, the orography and world stress map near the epicentral region. Main results are that a certain lithological selectivity can be recognized and that the known main stress field and seismogenic faults seem to be less important than certain tectonic lineaments, which are classified as non-seismogenic. The strong correlation between the topography and the TIR anomalies is in agreement with proposed physical mechanism for the generation of TIR anomalies. This relation is, in turn, present mainly in correspondence to two tectonic lineaments which in particular are thrusts: therefore, strong compressive states seem to be a positive condition for the generation of TIR anomalies. The temporary modification of these stress fields have triggered the Paganica Fault to its normal rupture mechanism. It is important to note that the distances, over which the TIR anomalies occurred, are an order of magnitude larger than the estimated length of the main fault rupture. Pixel-by-pixel time-series comparisons between the maximum TIR anomaly area and the epicentre of the main shock show that the increase in radiative emission occurred in the areas of maximum TIR anomalies and did not start by spreading outward from the epicentral region.

Geosphere coupling and hydrothermal anomalies before the 2009 <i>M</i><sub>w</sub> 6.3 L'Aquila earthquake in Italy

“…Following the preceding stable phase P1-1 and the fore part of P1-2 before the January in 2008, the b value drastically decreased as the mainshock approached. Figure 10 shows that the curve drops to the lowest point of b = 0.747 about 27 March 2009, i.e., ∼ 10 days before the mainshock or a few days before the occurrence of various thermal anomalies (Piroddi and Ranieri, 2012;Piroddi et al, 2014). Meanwhile, the entropy gradually increased to reach the peak (almost 0.2, Fig.…”

“…A unified lithosphere-atmosphere-ionosphere coupling (LAIC) model was proposed to explain the inherent links among different parameters (Liperovsky et al, 2008b;Pulinets and Ouzounov, 2011;Pulinets, 2012). This model has been verified by several case studies on the spatiotemporal features of the anomalies of multiple parameters (Pu- The FMS was obtained from the U.S. Geological Survey's National Earthquake Information Center (Di Luccio et al, 2010;Piroddi et al, 2014). (b) The main thrusts in Italy, with the black solid line box showing the geographical location of (a) (Benoit et al, 2011).…”

“…13a) used by Piroddi et al (2014) to show the variations in the b values with depth before the L'Aquila earthquake. Another section of equal length (section 2 in Fig.…”

Integrated Geophysical and Aerial Sensing Methods for Archaeology: A Case History in the Punic Site of Villamar (Sardinia, Italy)

“…The thermal processing method is based on the modification of an algorithm developed for geostationary satellite thermal data in environmental monitoring in order to evaluate the short-term seismic hazard based on a case study from the L'Aquila earthquake of 6 April 2009 [55][56][57].…”

Effects of seismic activity on the fluorescence signal of groundwater

“…Pre-seismic events such as thermal infrared emissions, surface temperature anomalies, radon irregularities and changes in physical and chemical properties of groundwater prior to major earthquakes have been reported (Tramutoli et al, 2005;Piroddi et al, 2014;Guangmeng, 2008, Ouzounov et al, 2006Singh et al, 2016;Biagi et al, 2000;Fidani et al, 2017). Anomalies in pH, conductivity or variations in ion content of groundwater can be explained through the interaction between positive holes and water (Grant et al, 2011).…”