This document involved the statistical analysis of natural water conductivity data (μS/cm) within the Mexican seismic coastal border with the purpose of contributing to the knowledge of the phenomena related to the precursor events of earthquakes. In this context, the possible connection between natural voltage and electromagnetic energy emanating from the Earth’s interior and the seismic activity in that region is evaluated.

The study of the electromagnetic energy related with the seismic activity, regularly has been addressed through evaluations of electromagnetic emission (EME) in the range of very, ultra-low and extremely low-frequency waves that reach the Earth surface through faults or unstable areas. This kind of radiation manifest their influence changing the local atmospheric electricity in the local ionosphere, and the activity level sometimes increases one week just before to an earthquake event, although with micro-seismic activity (<4 - 4.5 degrees), this kind of anomalies are monitored with the use of ground-based observations or remote sensing with satellite with the objective of detect plasma perturbations, thermal anomalies and radio emissions associated with EQs in the local atmosphere [1] - [8] ; with the atmospheric electricity changes occur heating and increasing the local relative humidity [9] [10] [11] [12] , changes that produce or leads occasionally to local luminous phenomena or earthquake lights (EQL), phenomenon commonly observed few weeks or hours before an earthquake, sometimes appears diffused light looking as reddish light ranging from orange to violet, others are halos having a dull rose colored luminosity, sky yellow light like an aurora or vapor with limited luminosity covering the local mountains, generally low-lying, just meters above the ground [13] [14] [15] [16] . The EME also influences the formation of aerosols and clouds and the presence of positive ions immersed within a charged atmosphere. The clouds anomalies regularly before an earthquake, show linear pattern along active faults that remain for hours without no movement, affecting several kilometers but disappear a few days after the event [17] - [23] . Although recurrently debated, this EME anomalies get influence the behavior of birds, fishes, mammals and including humans: animal responses to earthquake-related stimuli are varied, sometime is related to acoustic waves at low frequency, also aquatic animals are able to perceive electrical impulses; the strange behavior of animals sometimes is attributed to the environmental presence of pre-seismic EM emissions. In the case, human being frequently feel the discomfort in the ears or general physical inconvenience in the whole body: irritability, dizziness, insomnia, pain in the ears and migraines [10] [11] [24] - [30] .

The study of electromagnetic emissions (EME) as large earthquake short-term prediction involves very, ultra-low and extreme frequency electromagnetic emissions, and frequently this information is obtained by remote sensing. In this regard, the data more used in very studies was related to micro-satellite DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) designed expressly for Ionosphere perturbations linked to earthquakes, man-made transmitters, volcanoes and lightning [6] [31] [32] [33] [34] ; the mission satellite was retired on December 9, 2010 after more than 6.5 years on orbit (https://demeter.cnes.fr/fr/DEMETER/Fr/index.htm). Other research projects apply ground observation by mean of antennas, detectors and an analyzer system’s network.

As a complement of two previous studies [35] [36] , in the ambit of electromagnetic emissions study (EME) possibly emanating from the Earth’s interior layers, of indirect way and applying a micro-regional focus related to ground observation, from fourth trimester of 2014 it was conducted a data statistical research to evaluate these emanations, studying the possibly influence of EME on the water natural conductivity behavior and its possible relationship with earthquakes manifested during the time period of monitoring. The study area it was located on the Pacific coast of southern Mexico in a section considered the most seismic region on the coastal border in Oaxaca estate limits, this is located on the Pinotepa National municipality, particularly in a coastal community called “Corralero” [35] [36] [37] [38] [39] .

The monitoring and information gathered of the natural conductivity of water evaluated in the region from September 2014 to February 2015 [35] [36] , considering monitoring sites of low, moderate and high seismic activity, a research focus with no prior known antecedents until 2014. The results showed in that first step, the possible presence of patterns behavior in the data of natural conductivity, one of them pointed to the relationship existing between the geographical position of conductivity sensor and the seismic activity manifested during the monitoring period; to 290 kilometers far away from the coastal border, the presence of “atypical variations” of conductivity data (rare drops and peaks) was almost imperceptible and in the surroundings, few seismic occurred during the period of monitoring.

But within the coastal border between Guerrero and Oaxaca states, the atypical variations were self-evident and the presence of micro seismic activity was very significant (<4.0 Mw) Figure 2 at [35] . In addition, the data analyzed of the coastal border drove to another pattern, the subtle connection with the subsequent occurrence of seismic activity and the atypical variations of conductivity data, this behavior is possibly influenced by energy emanating from inside the Earth’s layers taking into account the possible high level of rock fracturing of the regional continental crust [37] .

The second step of area analysis studied from March to July, 2016, emphasized the comparison of natural water conductivity data of two wells [36] , both separated by 80 meters from each other, this focus showed other interesting patterns, one of them denoted the daily and frequent variation of natural conductivity possibly related to the internal flow of water, the groundwater movement is extremely fast indicating a vigorous groundwater recharge, possibly related to terrain compress or slight tilting of ground caused by very light earthquakes [10] [38] [39] . The analysis of multiple 24-hour data series sets showed another pattern: the noticeable oscillations of natural conductivity between 7:00 to 22:00 hours, possibly related to human activity but, this influence is not very clear and proved truthfully, Figure 11 at [36] . The last one pattern observed revealed that during the total data monitoring of conductivity through 61 days there were three significant variations of natural conductivity in different periods (May 15 to 23; May 31 to June 9 and June 15 to July 9) highlighting the last period because showed that during the water conductivity increase run-up, there was null seismic activity but when water conductivity decreased, the seismic activity increased considerably with seismic events more of them with Mw < 4, Figure 13 at [36] .

The main approach used in this document was based on the statistical analysis of the data of water natural conductivity (μS/cm) and its behavior trends, recorded by a conductivity sensor data-logger, and likely correspondence or correlation with subsequent seismic activity (<4.0 Mw) occurred to distance range of 50, 100, 150, 200, 250, 300, 350 and 400 kilometers far away of the sensor, as an indirect way to find out the possible presence of EME and its influence in the local environmental conditions, Figure 1. The data period analysis was from February 3 to April 15, 2015, at well CAW01, and from May 11 to July 17, 2015, at well CAW02, the total number of data recorded was 128,469 using a sampling frequency of 45 seconds; the reservoirs are located at the geographic coordinates 16˚14'10.6"N and 98˚11.406'W, and 16˚14'10.5"N and 98˚11'14.5"W; their dimensions correspond to 1 × 1 × 6 meters and 1.3 × 1.3 × 3 meters, respectively. The technical characteristics of sensor used, correspond to a non-contact capacitive sensor commercially called Data-logger HOBO U24-001, the details of the instrument technical specification used are in [35] [36] [40] . The 950 earthquakes occurred within continental and marine environment in 2015 in the territorial limits of Guerrero and Oaxaca states, Mexico, were acquired of the page Web of the Seismological National (SSN) Service of Mexico, http://www.ssn.unam.mx/.

In order to generate some graphs displaying the interaction of natural conductivity behavior and the seismic activity manifested in such periods above

mentioned, on average 128,469 records of natural conductivity of water and 950 earthquakes were analyzed and graphed; in complement, basics statistics such as minimum, maximum, mode and total earthquakes occurred and Fisher test, were obtained and applied.

The data statistical analysis of the natural conductivity behavior were carried out in two wells separated 80 meters from each other; each well was analyzed both in their spatial position between them and at different distance ranges, considering the position of the conductivity sensor and the earthquakes occurred during the same monitoring period, Figure 1. Taking into account the distance ranges of 50, 100, 150, 200, 250, 300, 350, 400 and 450 kilometers, separately for each well, the interactions of measured conductivity and earthquakes manifested in both the continental and marine environments were analyzed, as result 32 graphs of both environment were obtained, Figures 2-9 and Figures 10-17 correspond to site CAW01 in the continental and marine environment respectively; Figures 18-25 and Figures 26-33 correspond to site CAW02 in the continental and environment marine in the order given. So as to find out noteworthy dif-

ferences among data series with an ascending tendency and descending tendency of the natural conductivity behavior records, equally within the continental and marine environments too, both sets of data were graphic analyzed initially according the total earthquakes occurred in each distance range above mentioned (Figure 34 & Figure 35 and Table 1 & Table 2 to site CAW01 and Figure 36 & Figure 37 and Table 3 & Table 4 to site CAW02); in complement, to find out significant statistical differences among data, to the data series, the Fisher test was applied (Figure 38 & Figure 39 to site CAW01 and Figures 40-43 to site CAW02). The purpose of these last analysis aims to provide indirectly, evidence of the possible presence of energy flows in the surroundings previous to seismic activity and its possibly influence of natural water conductivity, effect probably related to the internal dynamics of the Earth’s deep layers linked with natural voltage and electromagnetic energy pulses that reach the surface by lithosphere fractures, pulses that could trigger the slight seismic activity within the study area [10] [18] [19] [36] [41] [42] [43] .

Within de study area, in the range of 0 to 50 kilometers, considered the most important range in terms of correlation between water natural conductivity (μS/cm) and seismic activity, the main characteristics of the earthquakes used in this research, correspond to micro-events to slight events (<4.5 Mw) and almost all are classified shallow (<70 km depth) and just two was intermediates (72 and 80 km depth) occurred to 21 and 28 kilometers far away from the sensor.

According to the accomplishment obtained, the study area call “Corralero” within the Pinotepa National municipality, demonstrate to be an area where the major quantity of earthquakes occur [35] [36] ; in a range of 50 kilometers around, this statement is unobjectionable (Figure 1, Tables 1-4 and Figure 18), beyond of this range, the number of earthquakes occurred drops outstandingly.

In a range of 50 kilometers round, the study area called “Corralero” within the Pinotepa National municipality, Oaxaca State, demonstrates to be an area where the major quantity of earthquakes occur, Figure 1 & Figure 2, Figure 18, Figure 34 and Figure 36. Correspond to micro-events to slight events (<4.5 Mw) and 98% are considered shallow manifested to <70 km depth and just one was intermediate with 72 km depth.

The spatial position of each well (CAW01 and Site CAW02) was decisive and determinant in the grade of influence of surrounding environment, and these effects can be related to the presence of aquatic environment and dynamic water mixing that affect the ions dissolved, this relationship is very clear in the conductivity behavior data recorded in Site CAW01 for closeness of coastal bodies of water. In this case, there were no significant statistical differences between data series, and the behavior was very similar in the continental and marine environment.

However, in the case of site CAW02, the influence of surrounding environment related to lithological barriers and regional and local stratigraphic units, affects different in the regional and local hydrological dynamics, so the water conductivity behavior data recorded in the site CAW02 is influenced possibly by local lithological and stratigraphic conditions, region that has a complex tectonic history of magmatism and metamorphism, with many discontinuities or weakness zones, because possibly the local crust is highly fractured [37] . Seemingly these surrounding environment conditions caused significant statistical differences among the main oscillations of conductivity records above described and possibly promote the slight seismic activity too [11] [41] [45] [46] [47] [48] . According to that, in general, within the continental environment, the range of 0 to 50 km showed the most important statistical significance, revealing to have the most number of earthquakes, Figure 40 & Figure 41, with higher values and more intensity, particularly when the tendency of conductivity data is descending. A very similar connection within the marine environment between the conductivity data behavior and seismic activity occurred during recording time was observed.

This research developed in the seismic coastal border limits of Guerrero-Oaxaca states, Mexico, was worked out with the intention of strengthening more in the knowledge of the previous events on the earthquakes and the possible connection between natural voltage and electromagnetic energy emanating from the inner layers of the Earth. Therefore, the data of natural water conductivity analyzed in this research seems to support this linkage taking in account the behavior of each conductivity record and the time trends; according to the results, the natural water conductivity data and more important trends recorded in the study area give the impression that occur before the seismic activity, Figures 18-25 and Table 3 & Table 4.

The author enthusiastically acknowledge the contributions to this research to Engineer José Francisco Hernández Pérez, Head of the Center of Proposed Draft of the South Pacific, regional office of the Coordination of Hydroelectric Projects (Federal Electricity Commission), for the logistic support, transportation, human and financial resources provided, without this decisive help would have been extremely difficult for ending this research. In the same way to Dr. Arturo Colín Cruz from the Faculty of Chemistry, Autonomous University of Mexico State, Toluca de Lerdo, Mexico, for his invaluable experience and professional guidance. Finally, to Andrés Suasto A. and Oscar E. González A, for their support, friendship and solidarity during the trips.

Martínez-García, F. (2017) Statistical Analysis of Natural Water Conductivity Data Behavior in Two Wells: Seismic Coastal Border Limits of Guerrero-Oaxaca States, Mexico. Open Access Library Journal, 4: e3900. https://doi.org/10.4236/oalib.1103900