The subduction zone of central Chile (36°S) has produced some of the world's largest earthquakes and significant volcanic eruptions. Understanding the fluid fluxes and structure of the subducting slab and overriding plate can provide insight into the tectonic processes responsible for both seismicity and magmatism. Broadband and long‐period magnetotelluric data were collected along a 350‐km profile in central Chile and Argentina and show a regional geoelectric strike of 15 ± 19° east of north. The preferred two‐dimensional inversion model included the geometry of the subducting Nazca plate as a constraint. On the upper surface of the Nazca plate, conductors were interpreted as fluids expelled from the downgoing slab via compaction at shallow depth (C1) and metamorphic reactions at depths of 40–90 km (C2 and C3). At greater depths (130 km), a conductor (C7) is interpreted as a region of partial melt related to deserpentinization in the backarc. A resistor on the slab interface (R1) is coincident with a high‐velocity anomaly which was interpreted as a strong asperity which may affect the coseismic slip behavior of large megathrust earthquakes at this latitude. Correlations with seismicity suggest slab fluids alter the forearc mantle and define the downdip limit of the seismogenic zone. Beneath the volcanic arc, several upper crustal conductors (C4 and C5) represent partial melt beneath the Tatara‐San Pedro Volcano and the Laguna del Maule Volcanic Field. A deeper lower crustal conductor (C6) underlies both volcanoes and suggests a connected network of melt in a thermally mature lower crust.

A profile of broadband magnetotelluric stations was acquired between 2009 and 2016 at 35°-36°S in the Southern Volcanic Zone of the Chilean Andes to image the subduction zone and its relation with the volcanic arc at this latitude. This transect extends from the Coastal Cordillera across the Central Valley and the volcanic arc of the Principal Cordillera to the Argentine border. Two active volcanic complexes are found along this profile: Tatara-San Pedro is located on the modern volcanic front, and the Laguna del Maule volcanic field is found approximately 30 km to the east. The latter exhibits considerable signs of unrest, such as uplift rates of up to 25 cm/year, and has produced a high concentration of silicic eruptions in the last 25 ky. The data covered the period range from 0.001 to 1000 s. Robust processing techniques were used, including remote reference, and dimensionality was investigated by estimation of geoelectric strike, skew and analysis of the induction arrows. The data were modeled using a 2D inversion algorithm to produce a resistivity model which was consistent with surface geology and seismicity. The final resistivity model shows a generally resistive fore-arc structure, coincident with the tectonic environment, and a wide conductive region from the volcanic front to the east. This suggests a broad region of magmatism throughout the arc, related to three distinct magma bodies, associated with the Tatara-San Pedro and Laguna del Maule volcanic complexes and the Mariposa Geothermal System.

With the advancement of the use of geophysical methods in mining exploration, the possibility of restudying known mineral deposits that could have greater potential than that previously estimated is opening up, as is the case in the Maricunga Belt (MB), which is a metallogenic belt located east of Copiapó, Chile, with a length of 200 km and oriented in the NNE-SSW direction. This belt hosts significant gold deposits classified as porphyry gold (-copper), epithermal gold (-silver) of a high sulphidation type, and transitional gold, in some districts. In this work we studied the characteristics of the MB through local earthquake tomography (LET), which revealed a clear spatial correlation between low Vp/Vs anomalies and the gold deposits, demonstrating that lithologic interpretation using Vp and Vs values of the seismic tomography makes sense for the most common rocks associated with the genesis of porphyry-type deposits. Furthermore, high Vp/Vs anomalies were correlated to the main regional faults around the study zone, which seem to have a robust structural control regarding the location of the deposits.

Estimates of the onset times of P phases from active source experiments can effectively be used in developing wavespeed models, and the large number of recordings typical of such experiments incentivizes the development of automated approaches to generate these estimates. The simplicity and repeatability of an airgun source such as that used in the 2016 Pisagua/Iquique Crustal Tomography to Understand the Region of the Earthquake Source (PICTURES) project in northern Chile suggested that a straightforward application of waveform cross-correlation would suffice for arrivals recorded by a network of inland seismic stations, but did not work well due to significant variations in waveform morphology. Application of an alternative algorithm typically used in passive source investigations, the Regressive ESTimator (REST) autopicking package, also proved unsatisfactory, largely because the limited spectral bandwidth of the airgun source and the frequent occurrence of local seismicity led to numerous false picks. This motivated the development of a new approach, named CORREL, that is a hybrid of REST and cross-correlation, with the addition of a constraint in the form of a polynomial function based on the REST picks that provides a reasonable prediction of an onset time. Compared to the results obtained originally from REST and simple waveform correlation, the application of CORREL to the PICTURES data both significantly increased the number of arrivals detected and greatly reduced the number of outliers. The predictive polynomial also provides CORREL a better means to discriminate true shots from the abundant natural seismicity.

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