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The Santa Lucía River Basin Trough is located in the southern sector of the Eastern Republic of Uruguay and has an area of almost 6,000 km2. In this work, the depth to the basement in the SW sector of the Santa Lucia Basin (SLB) was determined, using geophysical methods of exploration. The interest of exploring this geological basin is to determine its depth, recognizing the possible existence of deep aquifers, and the feasibility of hydrothermalism. For this reason were acquired, processed, inverted, and interpreted 10 magnetotelluric (MT) soundings. A 3D inversion based on the ModEM code was performed, and a 2D inversion (NLCG) of the invariant determinant along a profile that crosses the study area was carried out; their comparison yields similar resistivity and structural models results. The resistivity modeling was complemented with a Bouguer anomaly map created from a gravimetric database of 157 stations. Our geophysical results indicate that the Santa Lucia trough deepens toward the E-NE, reaching sedimentary thicknesses that may exceed 950 m. Outside the studied sector, its depth increases according to the gravity minimum, toward the NE of the area. Therefore, sandy or deep fractured episodes could harbor hot springs, whose temperature, considering the normal geothermal gradient of 30 °C/km, would approximately be in the range of 36–40 °C. [ABSTRACT FROM AUTHOR]

The Los Humeros volcanic complex, a 21 × 15 km diameter caldera edifice nesting volcanic domes and a complex faulting structure, is located at the eastern edge of the Trans-mexican volcanic belt (TMVB). It is a young edifice (<0.5 Ma) that hosts one of the five main geothermal fields of Mexico with still an important energy production (∼65 kW installed capacity). Being one of the more studied producing fields, the geothermal system of the caldera is largely unknown at depths greater than ∼2.4 km, which is the approximate penetration range of the available geothermal wells. Here we present the results of a geophysical survey in Los Humeros caldera and surroundings with the aim to provide further insight on the physical characteristics of the geothermal system at depths greater than 2.4 km. The survey comprised 70 broadband magnetotelluric (MT) soundings distributed within and in the periphery of the caldera edifice of which we present here three EW profiles. We also accomplished a mesh of 718 accurately leveled gravity stations. These data sets were complemented with 13 TDEM soundings for static shift control, as well as with the aero-magnetic digital chart of the area (#E14-3, SGM, 2004). The MT data analysis yielded an average electric azimuth of N23W for the central profile where the field production is concentrated, which is quite consistent with the mapped NW-SE geological structure. However, at individual frequency ranges the strike follows the local faulting structures, most of which are apparently controlled by the deeper crater structure. At the production zone, the conductivity model reveals the existence of an eastward dipping resistive body, which follows the isotherms registered at the wells. The inclined conductivity interface above it seems to play an important role in controlling the heat and fluid flow towards shallow depths. Petrographic studies of well samples provide evidence of mineralogical assemblages that suggest magnetite-metasomatose hydrothermal alteration. The production zone coincides with maximum gravity and magnetic gradients, at the western edge of the well-defined circular crater anomaly. At this point the central MT section (profile 1) shows the shallower depth (2–3 km) to the relatively high resistivity (∼400–500 ohm-m) and magnetized intrusive-like body. The interpreted geophysical and surface geological data backed by well data support a reservoir and plume model structure consisting of a resistive propylitic core that feds the geothermal field through fractures and deep- seated faults. Surface conductors associated with stratified mineralization produced from lixiviation of geothermal fluids are well differentiated from deeper conductors. The better preserved northern sector of the Humeros caldera yields an anomalous deep conductor at depths of 6–7 km below sea level (profile 5) as well as at the central production sector (profile 1) whereas the anomalous conductivity zone at the southern profile (profile 6) could be as shallow as 5 km below sea level. These anomalous conductivity zones are expected to be associated to the primary energy source of the Los Humeros geothermal system in the form of partial fusion or hypercritical trapped fluids within the upper crust, conditions that have been concluded to prevail along cordilleras of the American continent (e.g. Hyndman, 2017). [ABSTRACT FROM AUTHOR]

The objective of this study is the analysis of the south of Chicontepec Paleocanyon (PC) and the relation of electromagnetic anomalies. For this purpose, we measured, processed, and interpreted 16 broadband magnetotelluric (MT) soundings, disposed of in an orthogonal profile that covers the inside and the boundaries of the Paleocanyon. We performed a 3-D inversion of the data set (ModEM) using the range of periods between 10−3–102 s. In addition, we compared the result of 3-D inversion and the interpolation of 1-D inversion in their invariant rotational along the profile, where it is watched that they are similar in the resistivity anomalies and geological structures. The interpretation of the 3D resistivity inversion model shows the heterogeneous geometry and boundaries of the Paleocanyon and the contact between sediments and the top of the basement. Furthermore, based on the resistivity contrast, the information from wells-drilled, and seismic sections, it is possible to delimitate some anomalies that perhaps have the probability of hydrocarbon existence. • Comparison of sections 3D MT inversion and seismic in the Chicontepec Paleocanyon. • Resistive contrasts were correlated to the geological structures and the basement. • 3D Magnetotellurics is a powerful technique for oil and gas exploration • MT surveying can help seismic information to detect oil/gas reservoirs [ABSTRACT FROM AUTHOR]

In this study, we investigated correlations between electromagnetic and seismic signals of the 2017 February 15 Veracruz, Mexico, earthquake (M w = 4.8). We carried out a time–frequency misfit analysis based on the continuous wavelet transform in order to compare electric, magnetic and seismic records accurately. This analysis was performed for horizontal and vertical components separately. Our results from time–frequency misfit and goodness-of-fit criteria confirm the general similarity between seismic and electromagnetic signals both in frequency and time. Additionally, we studied the behaviour of peak amplitudes of seismoelectromagenetic records as a function of magnitude and distance. Our observations are in good agreement with previous studies, confirming scaling with magnitude and attenuation with distance. Radiated seismic energy estimations were performed with two methods: integration of velocity records and empirical Green function, respectively. Estimated energy magnitudes (4.35 <  M e < 4.98) are consistent with reported seismic magnitudes for this event. We propose a method for determining electric and magnetic coseismic energies based on the concept of energy flux as implemented in the frequency domain by the integration of electromagnetic records. The calculated energies showed that the radiated seismic energy is much higher than the electric and magnetic energies. [ABSTRACT FROM AUTHOR]