Arc volcanoes are fed by complex networks of storage zones that extend throughout the crust. Though the geometric details of these transcrustal magmatic systems are well resolved beneath several volcanic settings, the relationship between magma transport at depth and volcanic unrest at the surface remains poorly understood. At Laguna del Maule in central Chile, we show that seismically imaged magma reservoirs in the upper and lower crust are connected by a zone of deep crustal seismicity. A pronounced one-day seismic swarm in 2018 was followed approximately 3 months later by an increase in surface uplift rate. We infer that this swarm was driven by the injection of new melt, transported between lower to upper crust magma reservoirs. The lag time between melt transport and surface acceleration was perhaps governed by the hydraulic diffusivity within the upper crustal reservoir. These results indicate that volcanic unrest begins deep within the crust and months before observable signals of shallow reservoir pressurization. An integrated assessment of receiver function imaging, seismicity, and geodetic data suggests surface uplift at Laguna Del Maule, Chile, was preceded by a one-day seismic swarm in 2018, caused by magma ascending between reservoirs in the upper and lower crust.

The Andean Margin hosts alternating regions of “flat” and “normal” subduction, which includes the Pampean flat slab that extends from central Chile to Argentina. The discovery of an unusual travel time anomaly beneath the high Andes above the flat slab motivated a study to investigate the lithosphere in this region. Leveraging extensive archived seismic data from both Chile and Argentina, we performed a large-scale joint inversion of P and S body wave arrival times from earthquakes, and surface wave dispersion measurements from earthquakes and ambient noise. We created 3D Vp, Vs and Vp/Vs models using at least an order of magnitude more data than previous studies with about an 80% reduction in grid spacing. Our models corroborate results from previous studies: (1) a high velocity, high Vp/Vs region associated with a cool, slightly hydrated and depleted mantle above the flat slab, and (2) a low velocity structure beneath the high Andes interpreted as an overthickened crustal root, with our results showing that the root extends to just above the flat slab. Curiously, our models also reveal two low velocity zones within and below the flat slab seismic zone that have not been previously reported. Notably, the decrease in velocity is more pronounced in Vp than Vs. We postulate that the eastern low velocity anomaly is likely due to hot asthenosphere heating the slab, although no melting is occurring as the Vs is not significantly reduced. The western low velocity anomaly, which spatially correlates with the Juan Fernandez Ridge (JFR), we postulate is either due to the presence of supercritical fluids trapped within the JFR or an increase in silica content possibly linked to petit spot volcanism.

Abstract Seamounts and ridges are often invoked to explain subduction‐related phenomena such as flat slab generation, but the extent of their involvement remains controversial. An analysis of seismicity in the region of the Pampean flat slab through an application of an automated catalog generation algorithm resulted in 35,924 well constrained local earthquake hypocenters and a total of 12,172 focal mechanisms. Several new features related to the subduction of the Juan Fernandez Ridge (JFR) were discovered, including (a) a series of parallel lineaments of seismicity in the subducted Nazca plate separated by about 50 km and trending about 20°, and (b) a strong spatial correlation between these deeper (>80 km depth) regions of intense seismicity and concentrations of activity in the crust almost directly above it. Focal mechanisms of the deeper events are almost exclusively (∼81%) normal, while those in the crust are predominantly (∼70%) reverse. The deeper lineaments mirror the orientation and spacing of several seamount chains seen on the Nazca plate, suggesting that these patterns are caused by the same types of features at depth. This would imply that relatively minor features persist as slab anomalies long after they are subducted. The correlation of the deeper seismicity that defines these features with seismicity in the mid to lower crust suggests a genetic relation between the two. We postulate that volatiles from the subducted ridges percolate into the South American crust and induce seismicity essentially by fracking it.

This repository includes: 1. A gzipped automated catalogue of earthquake locations with P and S arrival times for the SIEMBRA and ESP networks in South America 2. A README explaining the information in each column

This repository includes: 1. Gzipped automated catalogues of earthquake locations with P and S arrival times for: The CHARGE network - charge.data.gz The CHARSME and CSN networks - charsme_csn.data.gz 2. A README explaining the information in each column