Reyes-Wagner Valentina, Díaz Daniel, Cordell Darcy, Unsworth Martyn
1Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile.
Centro de Excelencia en Geotermia de Los Andes, Plaza Ercilla 803, Santiago, Chile.
Earth Planets Space. 2017;69(1):142. doi: 10.1186/s40623-017-0726-z. Epub 2017 Oct 12.
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.
2009年至2016年期间，在智利安第斯山脉南部火山带南纬35°至36°之间获取了一条宽带大地电磁测深站剖面，以成像俯冲带及其与该纬度火山弧的关系。该剖面从海岸山脉延伸穿过中央山谷和主要山脉的火山弧，直至阿根廷边境。沿此剖面发现了两个活火山复合体：塔拉-圣佩德罗位于现代火山前沿，而毛莱湖火山区位于其东侧约30公里处。后者表现出相当多的不稳定迹象，如每年高达25厘米的隆升速率，并且在过去25千年中产生了高浓度的硅酸岩喷发。数据涵盖了从0.001秒到1000秒的周期范围。使用了稳健的处理技术，包括远程参考，并通过估计地电走向、倾斜度和分析感应箭头来研究维度。数据使用二维反演算法进行建模，以生成与地表地质和地震活动一致的电阻率模型。最终的电阻率模型显示，与构造环境一致，弧前结构总体呈高电阻，从火山前沿向东有一个广阔的导电区域。这表明整个火山弧存在一个广泛的岩浆活动区域，与三个不同的岩浆体有关，分别与塔拉-圣佩德罗和毛莱湖火山区以及马里波萨地热系统相关。
