
Gerd SielfeldUniversity of Auckland · School of Environment
Gerd Sielfeld
Doctor of Engineering
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20
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Introduction
Pleased to have been born and grown up in one of the most mesmerizing tectonic settings. A years-long forged passion for the Andes conducted me into geoscience. Since 2008 I have been working in active volcanic chains using structural geology as a fundamental tool to understand the nature of fluid-flow in ancient and active hydrothermal systems.
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Publications
Publications (20)
The Southern Patagonian Icefield (SPI) lies above an area of slow convergence between Antarctic and South-America plates, where limited seismicity is recorded by global or regional seismic networks. To understand the seismic behavior of this zone, we analyze two years of continuous broad-band data recorded by 27-seismometers, deployed around the SP...
Decoding means decrypting a hidden message. Here, the encrypted messages are the state of stress, fluid pathways, and volcano tectonic processes occurring in volcanoes of the Andean Southern Volcanic Zone (SVZ). To decode these messages, we use earthquake focal mechanisms, fault slip data, and a Monte Carlo simulation that predicts potential pathwa...
Volcano seismology is an essential tool for monitoring volcanic processes in the advent and during eruptions. A variety of seismic signals can be recorded at volcanoes, of which some are thought to be related to the migration of fluids which is of primary importance for the anticipation of imminent eruptions. We investigate the volcanic crises at V...
Volcanic cones are frequently near their gravitational stability limit, which can lead to lateral collapse of the edifice, causing extensive environmental impact, property damage, and loss of life. Here, we examine lateral collapses in mafic arc volcanoes, which are relatively structurally simple edifices dominated by a narrow compositional range f...
Since December 2018, the first seismic network deployed around the Austral Andes and its Southern Patagonian Ice Field is recording passive seismicity at the western margin of Southern Patagonia, Southernmost South America. Here, active tectonics is dominated by the interplay between the Antarctic plate's subduction at the trench and the sinistral...
Magma is transported through the lithosphere as dykes which, during periods of unrest, may feed eruptions at the surface. The propagation path of dykes is influenced by the crustal stress field and can be disturbed by crustal heterogeneities such as contrasting rock units or faults. Moreover, as dykes propagate, they themselves influence the surrou...
Oblique-slip tectonics in the intra-arc region of the Southern Andes accommodates heterogeneous deformation derived from plate convergence during the Pliocene and Quaternary. Long-term mechanical interaction between Andean transverse faults (i.e. NW-striking sinistral faults) and margin-parallel faults (i.e. NNE-striking faults) results in linked t...
Networks of fractures in the upper crust can act as pathways for fluids when they are optimally oriented. In some circumstances the coalescence and dilation of fractures in and around faults can play a key role in the transport, emplacement, and eventual eruption of magma at the surface. It is then relevant to assess the extent to which pre-existin...
The emplacement of many epithermal ore deposits is enabled by fault-fracture networks at different scales. Epithermal fluids make use of these anisotropies, while dynamically and spatially modifying their thermodynamic state-variables. Furthermore, new techniques are being developed nowadays to constrain the spatial distribution of high-grade areas...
We examine the intra‐arc crustal seismicity of the Andean Southern Volcanic Zone. Our aim is to resolve interseismic deformation in an active magmatic arc dominated by both margin‐parallel (Liquiñe‐Ofqui fault system, LOFS) and Andean transverse faults. Crustal seismicity provides information about the schizosphere tectonic state, delineating the g...
Dikes are thought to be the most efficient way of transporting magma through the upper crust and are the prevailing feeding mechanism of volcanic systems. As they propagate, dikes may either occupy existing fractures or create their own (as in Andersonian dikes), and so, can be found randomly or systematically oriented. Whereas Andersonian dikes ar...
Dykes and minor eruptive vents are not randomly distributed within tectonically controlled volcanic arcs, which is reflected in the resulting morphology of stratovolcanoes. As a first-order approach, regional stress field controls the spatial distribution and geometry of dykes and minor eruptive vents. However, favourably oriented pre-existing weak...
The Andes is the largest undeveloped geothermal region in the world. The Chilean case is the most
puzzling because the country is largely dependent on imported fuels causing, among other issues, high energy prices and energy dependency. But even though it has large quantities of geothermal resources which have been explored since the 1920s, no geot...
Tras el megaterremoto de subducción Mw 8.8. del 27 de Febrero del 2010, una secuencia de sismos de intraplaca en la región del antearco andino, dominada por dos eventos principales (Mw 6.9 y 7.0) ocurridos el 11 de marzo, puso de manifiesto la reactivación de la Falla Pichilemu. Ésta, previamente reconocida en superficie como un lineamiento morfoló...
One fundamental problem in continental margin tectonics is the nature of the interplay between tectonics and magma/fluid transport through the lithosphere. Deformation-driven fault-fracture networks have been regarded as efficient pathways through which magma and/or hydrothermal fluids are transported, stored and eventually connected to the earth s...
Uranium-thorium (U-Th) isotope compositions of whole rocks, groundmasses and minerals from mafic to intermediate Andean arc magmas were determined to assess the influence of crustal stress on rates of pre-eruptive crystallization and the significance of crystal uptake. Volcanoes investigated include Lascar in the central Andes, situated in a compre...
The Mariposa Geothermal System (MGS) is located 300 km south of Santiago, Chile, and has an inferred resource of 320 MWe. The field is outlined by a low resistivity MT anomaly with two lobes (or wings) that appear to relate to a clay cap associated to two principal upflow areas. The resource depth varies approximately 700 m to over 1000 m depending...