Gas hydrate occurrence and Morpho-structures along Chilean margin

• Main Author: Vargas Cordero, Ivan De La Cruz
• Other Authors: Fanucci, Francesco, Tinivella, Umberta
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Università degli studi di Trieste 2009
• Subjects: BSR; Chilean margin; geothermal gradient; gas hydrate; SCIENZE AMBIENTALI (AMBIENTE FISICO,MARINO E COSTIERO); GEO/10 GEOFISICA DELLA TERRA SOLIDA; Fernandez; permafrost
• Online Access: http://hdl.handle.net/10077/3207

2007/2008 During the last decades, the scientific community spent many efforts to study the gas hydrates in oceanic and permafrost environments. In fact, the gas hydrate occurrence has a global significance because of the potential energy resource represented by the large amount of hydrocarbon trapped in the hydrate phase. Moreover, it may play a role in global climate change, and it is also study because of the hazard that accumulations of gas hydrate may cause to drilling and seabed installations. In seismic data, the base of the gas hydrate presence is detected by a strong reflector, called BSR. Along the Chilean continental margin, in the last decades the BSR is well reported by several geophysical cruises. In particular, the BSR is recognized along the accretionary prism. An important aspect related to the gas hydrates is the estimate of gas concentration in the pore space by using seismic data. In fact, both compressional and shear wave velocities provide information about the presence of gas hydrate and free gas in marine sediments. A quantitative estimate of gas hydrate and free gas concentrations can be obtained by fitting the theoretical velocity to the experimental velocity. For this purpose, in this Thesis several seismic data are analyzed in order to detect, quantify and explain the gas hydrate presence in this region. Frontal and basal accretions were identified by interpreting six post-stack time migrated sections, which across the entire margin (continental shelf, continental slope, oceanic trench and oceanic crust). The trench infill southwards of Juan Fernandez Ridge is characterized by a succession of reflectors with high and low amplitude associated to turbidites. A thinner bed (0.3 s) was recognized in correspondence to the accretionary prism characterized by several morphological highs. These morphological highs were associated to different accretional stages. On the contrary, a thicker bed (0.8 s) was recognized in correspondence to an uplifted accretionary prism characterized by a ...