Monitoring of Gas Emissions in Light of an OEF Application

Abstract

This study analyzes the possibility to use geophysical and geochemical parameters in an OEF (Operational Earthquake Forecasting) application correlated with short-term changes in seismicity rates using a magnitude–frequency relationship. Tectonic stress over the limits of rock elasticity generates earthquakes, but it is possible that the emission of gases increases as a result of the breaking process. The question is how reliable is the emission of radon-222 and Carbon Dioxide (CO2), with effects on air ionization and aerosol concentration, in an OEF application? The first step is to select the seismic area (in our study this is the Vrancea area characterized by deep earthquakes at the bend of the Carpathian Mountains), then determine the daily and seasonal evolution of the forecast parameters, their deviations from the normal level, the short-term changes in seismicity rates using a magnitude–frequency relationship and finally to correlate the data with recorded seismic events. The results of anomaly detection, effect evaluation and data analysis alert the beneficiaries specialized in emergency situations (Inspectorate for Emergency Situations, organizations involved in managing special events). Standard methods such as the standard deviation from the mean value, time gradient, cross correlation, and linear regression are customized for the geological specificity of the area under investigation. For detection we use the short-time-average through long-time-average trigger (STA/LTA) method on time-integral data and the daily–seasonal variation of parameters is correlated with atmospheric conditions to avoid false decisions. The probability and epistemic uncertainty of the gas emissions resulting from this study, in addition to other precursor factors such as air ionization, time between earthquakes, temperature in the borehole, telluric currents, and Gutenberg Richter “a-b” parameters, act as inputs into a logical decision tree, indicating the possibility of implementing an OEF application for the Vrancea area. This study is novel in its analysis of the Vrancea area and performs a seismic forecasting procedure in a new form compared to the known ones.

Implementation of a Radon Monitoring Network in a Seismic Area

“…The processing methods were described in our articles [4,5]. Figure 9 is an example of how seismic activity correlates with radon emission.…”

“…Detection of variations in integrated radon variations from Plostina (Table 1) are presented in Figure 9(8). Seismic forecasting is possible by overlapping trigger areas (red dots in Figure 9) and using other precursor factors (CO2, air ionization, magnetic field, telluric field, infrasound, and atmospheric electrostatic field) [5].…”

“…Each monitoring station also has a weather station installed to decide whether radon emission anomalies are caused by weather conditions [18,19]. For this reason, the annual, seasonal, and daily variations of radon are determined in order to eliminate them from the category of anomalies [5].…”

“…They can consider the median values from Table 2, such as the background. In [5], we made an analysis for daily, seasonal, and yearly variations of radon. The scientists could take the data and define a period of time and consider the median value (for example) such as the background.…”

“…The monitoring of radon has an important place ( 222 Rn), as it is of interest in terms of population health, as well as being a seismic precursor factor. The relationship between seismicity and radon emission has been presented in many articles, including with reference to the area where our network, Vrancea, was implemented (for example [1][2][3][4][5][6][7][8]). In this work, the emphasis is on network implementation and solving the problems that have arisen in changing radon monitoring from an offline to an automatic process, in accordance with the requirements of the geophysical platforms to which it transfers data.…”