Investigation of Fluid-Seismic Processes Associated with the Bayou Corne, LA Sinkhole

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项目编号	1447006
	Investigation of Fluid-Seismic Processes Associated with the Bayou Corne, LA Sinkhole
	Douglas Dreger
主持机构	University of California-Berkeley
项目开始年	2015
	2015-02-01
项目结束日期	2017-01-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	107746(USD)
国家	美国
语种	英语
英文摘要	In June of 2012 the residents of Bayou Corne, Louisiana began reporting the occurrence of earthquakes, and unusual gas bubbling in the local waters. The USGS deployed broadband seismic instruments in the region and confirmed that a swarm of shallow earthquakes was occurring near the west flank of the Napoleonville Salt Dome. On August 2, 2012 a sinkhole formed at the location, filled with a slurry of water, crude oil and debris, leading to a declaration of emergency and evacuation of nearby residents. Preliminary analysis of the seismic records revealed that the individual earthquakes have a source signature that indicates a volume increase, which is believed to be due to high-pressure fluid and gas migrating from the deeper reservoirs to the surface through rock fractures resulting from the collapse of a side wall cavern in the salt dome. Many of the seismic records for earthquakes at Bayou Corne share features that are observed in volcanic and geothermal systems in which fluids at depth can generate a variety of earthquake and tremor phenomena. The study of the Bayou Corne seismicity will shed light on fluid-controlled seismic source mechanisms, and the investigation of how the seismic signals changed over time will lead to understanding of how the system evolved, and the process of failure that lead to the formation of the sinkhole. The methods employed and refined through the course of the study will more broadly improve seismic monitoring capability and hazard assessment associated with ongoing mining, oil and gas production, wastewater disposal, as well as the monitoring of volcanic activity. Through the course of the project the thousands of small (magnitude 0 to 2) earthquakes in the weeks prior to the formation of the sinkhole, and continuing afterward will be investigated. A method in which the seismic signals are continuously scanned enabling the autonomous detection, location and estimation of seismic source parameters used to determine full seismic moment tensors that are capable of resolving both shear and tensile components that will inform on the nature of deformation occurring in the system and the importance of gas-charged fluids in the seismic source process. Preliminary work utilized simplified one-dimensional seismic velocity models to describe the wave propagation from source to receiver, however the geology in salt dome environments is very complex, and the proposed research will utilize a three-dimensional seismic velocity model, and appropriate numerical codes, to generate three-dimensional propagation transfer functions to improve the imaging of the earthquake source mechanisms. In addition to the micro earthquakes there are observations of harmonic tremor that are similar to volcanic tremor and indicate a process of fluid migration through a network of fractures. There are also long-period (20s) tremor in which preliminary modeling has suggested they are the temporal pulsing of a volumetric source. There are even longer period signals that can be interpreted as broad tilting of the ground. The diverse signals will be modeled with fluid-crack dynamic models and other mechanical models to investigate the relationships between them, and to the failure process of the geologic materials within and adjacent to the salt dome, and the formation of the sinkhole.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/67529
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Douglas Dreger.Investigation of Fluid-Seismic Processes Associated with the Bayou Corne, LA Sinkhole.2015.