Time series analysis of soil radon in Northern Pakistan: Implications for earthquake forecasting

Implication of Radon Monitoring for Earthquake Surveillance Using Statistical Techniques: A Case Study of Wenchuan Earthquake

“…In particular, the CEA is operating a very dense radon monitoring network for the surveillance of earthquake activity. For earthquake forecasting research, Rn is more preferred due to its comparatively longer half-life and easy detectability [14]. In the current study, we have analysed the variations of continuous groundwater Rn concentration associated with the devastating Wenchuan earthquake (May 12, 2008; Mw 7.9) at 9 stations over the whole year (2008) in the proximity e n s h a n r e g i o n Q in g c h u a n fa u lt J i a n g y o u -g u a n g y u a n f a u l t J i a n g y o u -g u a n x i a n f a u l t of the event epicentre.…”

“…The dynamics of the Rn time series show a very complex nonlinear temporal pattern normally characterized by nonstationary and multiscale features [52]. This chaotic regime of the time series is realized through diurnal, seasonal, multiyear, and decadal Rn cycles along with key influencing parameters [14,53,54]. Therefore, the Rn time series is subjected to fractal estimates to determine the degree of chaotic behaviour of Rn and intrinsic long-memory correlations, if any [55].…”

“…Persistency exhibits that a long-lasting autocorrelation exists within the time series, which implies that high present values will probably be followed by high future values and vice versa. And random walk means that they are uncorrelated or do not possess long memory trend [14,56].…”

“…Therefore, it is imperative to conduct research in this direction to mitigate the associated geohazards and minimize the loss of life and property. In this regard, numerous retrospective studies highlight the presence of atmospheric, ionospheric, and hydrogeochemical processes accompanied by earthquake activity [5][6][7][8][9][10][11][12][13][14][15][16]. These accompanying processes are considered as earthquake precursors and observed globally [11,14,[17][18][19][20][21][22][23].…”

“…The hydrogeochemical studies mainly include the monitoring in water level changes, Rn variability in either air, soil, or groundwater, an emanation of soil gases (CO 2 , CH 4 , and He), and other constituents such as Cl − , SO 2− 4 , and HCO − 3 are also used as a forerunner to access the earthquake-induced changes [7,10,11,[24][25][26][27]. However, the use of Rn is globally preferred in comparison with other precursors due to its relatively long half-life and ease of predictability [14].…”