Toward the development of a multi parametric system for a short-term assessment of the seismic hazard in Italy

Nicola Genzano,Carolina Filizzola,Mariano Lisi,Nicola Pergola,Valerio Tramutoli

doi:10.4401/ag-8227

Abstract

With the aim to develop a multi-parametric system devote to improving our present capability to assess seismic hazard particularly in the short-medium term, the preliminary step is to identify those parameters that have demonstrated their non-casual relation with earthquake occurrences and whose anomalous variations can be associated to the complex seismic process. Since 80, fluctuations of Earth thermally emitted radiation, measured by satellite sensors in the Thermal InfraRed (TIR) spectral region, have been reported by several authors in some connection with the occurrence of earthquakes; they and can be considered as one of the possible parameters to include within a multi-parametric system. In this paper, the Robust Satellite Techniques (RST) approach has been exploited to highlight Significant Sequences of TIR Anomalies (SSTAs) possibly related to seismic events happened in Italy in the period June 2004 - December 2014. In particular, we evaluated the level of correlation between occurrence of earthquakes with M≥4 and RST-based TIR anomalies using two different spatial resolutions of MSG-SEVIRI (Meteosat Second Generation -Spinning Enhanced Visible and Infrared Imager) images. Results of the two RST analyses show that the 82% of the identified SSTAs does not disappear when downscaled spatial resolution SEVIRI TIR records were used. For both analyses, more than 60% of SSTAs is apparently in connection with the occurrence of M≥4 earthquakes; more than the 80% of them has tendency to anticipate the occurrence of earthquakes. Although about the 40% of SSTAs is not apparently related to documented seismic activity (false positives), results of random tests (i.e. Molchan’s error diagrams) indicate a non-casual correlation between SSTAs and earthquake occurrences. These results confirm that the parameter “RST-based satellite TIR anomalies” is one of the possible candidates to be included in a multi-parametric system for time-Dependent Assessment of Seismic Hazard (t-DASH).

Highlights

The occurrence of even destructive earthquakes in areas that until were not considered at high seismic hazard, on the basis of probabilistic maps, highlighted the weakness of approaches such as the Probabilistic Seismic Hazard Analysis [PSHA; Cornell, 1968], widely used for almost 50 years but never validated by objective testing [Mulargia et al, 2017]
By applying the aforementioned rules to all Thermal Anomaly Map (TAM) obtained by applying the Robust Satellite Techniques (RST) methodology and computing both the traditional RETIRA index and the new proposed RETIRAbox index, in the period June 2004 - December 2014, 33 Sequences of TIR Anomalies (SSTAs) have been identified by using the RETIRA index and 28 SSTAs using the RETIRAbox index
The remaining 6 SSTAs disappear when RETIRAbox is used because STAs do not satisfy the requirements of relative intensity and/or persistence in space-time domain; on the contrary only 1 SSTA has been identified by using RETIRAbox but it is not is identified by using the traditional RETIRA index

Summary

Introduction

The occurrence of even destructive earthquakes in areas that until were not considered at high seismic hazard, on the basis of probabilistic maps, highlighted the weakness of approaches such as the Probabilistic Seismic Hazard Analysis [PSHA; Cornell, 1968], widely used for almost 50 years but never validated by objective testing [Mulargia et al, 2017]. From such analyses it will be possible to quantitatively characterize the predictive capabilities (in terms of successful forecasts, false positive rates and/or missed events) of each parameter with reference to specific regions, alerted space-time volumes, expected earthquake magnitudes, etc Good examples of such long-term correlation analyses are represented by studies concerning variations of the plasma frequency at the F2 peak foF2 of ionosphere during 1994–1999 [Liu et al, 2006], Ultra Low Frequency (ULF) geomagnetic signals over a 10-year period [Han et al, 2014], ionospheric ion density recorded by DEMETER satellite during more than 6 years [Li and Parrot, 2013] and, more recently, Earth’s thermally emitted radiation [Eleftheriou et al, 2016]. Results will be compared and random tests (Molchan diagram) will be performed in both cases to assess the lack of randomness in the appearance of RST-based TIR anomalies

RST methodology and RETIRA index

Results

Conclusion