The Pollino 2012 seismic sequence: clues from continuous radon monitoring

Abstract

Abstract. The 2012 Pollino (Calabria, Italy) seismic sequence, culminating in the Mw 5.2 earthquake of 25 October 2012, is investigated, exploiting data collected during a long-term continuous radon monitoring experiment performed in the epicentral area from late 2011 to the end of 2014. We analyse data collected both using a phenomenological approach based on quantitative evidence and a purely numerical analysis including the following: (i) correlation and cross-correlation investigations; (ii) an original approach aimed at limiting the impact of meteorological parameters variations on the interpretation of measured radon levels; (iii) a change point analysis; (iv) the implementation of an original detection algorithm aimed at highlighting the connections between radon emission variations and major seismic events occurrence. Results from both approaches suggest that radon monitoring stations can be subject to massive site effects, especially regarding rainfall, making data interpretation harder. The availability of long-term continuous measurements is crucial to precisely assess those effects. Nevertheless, statistical analysis shows a viable approach for quantitatively relating radon emanation variations to seismic energy release. Although much work is still needed to make radon time series analysis a robust complement to traditional seismological tools, this work has identified a characteristic variation in radon exhalation during the preparation process of large earthquakes.

Variasi Gas Radon dan Aktivitas Kegempaan di Sekitar Patahan Opak

“…Penelitian terbaru menunjukkan bahwa anomali gas radon dengan periode yang lebih lama berkorelasi positif dengan kejadian gempa yang akan datang dengan kekuatan yang lebih besar (Fu drr., 2017). Analisis statistik juga menunjukkan hubungan antara variasi gas radon terhadap pelepasan energi gempa (Piersanti drr., 2016). Konsentrasi gas radon di dalam tanah juga memiliki korelasi kuat dengan lokasi patahan (Lopez drr., 2016).…”

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“…Они обусловливают значительную зашумленность (the noise component) исходных данных, затрудняющую выделение предвестниковых аномалий. Это заставляет применять специальные методы выделения предвестниковых аномалий [Giuseppina, Morelli, 2012;Piersanti et al, 2016; Фирстов и др., Паровик, 2014].…”

“…They condition the significant noise component of the initial data, which makes it difficult to distinguish the precursor anomalies. This forces to use special methods for precursor anomalies identifying [Giuseppina, Morelli, 2012;Piersanti et al, 2016;Parovik, 2014].…”

“…The RVA began to increase in the water of the artesian well for 4.5 months before the Tohoku (Japan) megaearthquake on March 11, 2011 with M w = 9.0 and continued to grow after it. The total duration of the anomaly amounted for eight months [Tsunomori et al, 2011].…”

Diurnal and Semidiurnal Cyclicity of Radon (222Rn) in Groundwater, Giardino Spring, Central Apennines, Italy

“…In this study, we used Rn and groundwater table data from the Sulmona plain (i.e., the Giardino Spring for Rn monitoring and the PF 60.3 well for hydrogeological monitoring; see Figure 1a) to examine their cyclic and noncyclic variations. Determining the complete set of possible natural variations of Rn in groundwater is the fundamental prerequisite of using Rn as a tracer, or even precursor, of natural processes, including the seismic cycle and strong earthquakes [32][33][34][35]. Indeed, as the study area is strongly seismic [28], we have installed a Rn monitoring station in the attempt of identifying the long-term behavior of Rn in relation to the seismic cycle.…”