Creating a New Seismic Instrument from EarthScope Strainmeter Installations

GSTDTAP

项目编号	1460377
	Creating a New Seismic Instrument from EarthScope Strainmeter Installations
	Charles Langston
主持机构	University of Memphis
项目开始年	2015
	2015-06-15
项目结束日期	2017-05-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	157925(USD)
国家	美国
语种	英语
英文摘要	A major part of the National Science Foundation's EarthScope program facility is the Plate Boundary Observatory located along the Pacific coasts of the continental U.S. and Alaska. 74 borehole strainmeters have been installed as part of the Plate Boundary Observatory and collect ground deformation data that pertain to natural earthquake processes along the major fault systems of California, Oregon, and Washington states. Strain signals recorded by these systems depend on the conditions of the rock that immediately surrounds the borehole at depths of 500 feet or more in addition to the engineering details of how the instrument was cemented into the borehole. Unlike other geophysical instruments, borehole strainmeters must be calibrated after they have been installed to make sense of the resulting data. Scientists from the University of Memphis and UNAVCO, the major facilities operator, will be developing a method to calibrate these strainmeters by using seismic signals recorded by seismic instruments that have been installed with nearly all strainmeters. These methods will be developed for strainmeters within the ANZA seismic network of southern California and will also rely on data collected by two additional seismic array experiments. One has been installed at the Pinyon Flat Observatory run by the University of California, San Diego and at other by UNAVCO at selected strainmeter sites within the ANZA network. Calibration of these instruments is an invaluable service to the scientific community but, more importantly, calibrated and co-located seismic and strain instruments allow a new scientific use of this EarthScope facility through recently developed theory of seismic wave propagation. Each strainmeter/seismic instrument combination can take the place of a large specialized array of seismic instruments to determine the direction and speed of seismic waves generated by local earthquakes. This can allow a network of borehole strainmeters to be used as a network of seismic arrays to quickly locate and characterize an ongoing large earthquake. This can have great societal benefit for Earthquake Early Warning on the west coast. This collaborative project between the University of Memphis and UNAVCO will result in analytic methods for efficiently calibrating Plate Boundary Observatory (PBO) Gladwin Tensor Strain Meters (GTSMs) using seismic data from earthquakes. The investigators will extend methods previously developed by the University of Memphis that incorporate computation of reference, regional strain fields using seismic wave gradiometry for large earthquakes recorded by the ANZA southern California network. The present research will develop a method that incorporates a single three-component seismic sensor co-located with a GTSM to estimate strains from earthquake observations using wave gradiometry concepts rather than using a large array of seismic sensors. UNAVCO has installed 3 broadband seismometers at PBO GTSMs in the ANZA network to augment existing broadband/GTSM installations and UCSD has installed a dense, broadband array of 13 sensors within the area of the Pinyon Flat facility. Earthquake data from these new and existing co-located instruments will be used to estimate reference seismic strains that are then related to measured gauge strains by the GTSMs. An essential constraint in developing this method is that the ANZA GTSMs have been previously calibrated using the array method giving control on evaluating the success of the single station method. Data from the short-period seismometers installed with the GTSMs will also be incorporated in this work with the goal of using this existing data set to calibrate any other PBO strain meter without additional fieldwork. The over arching scientific goal of this project is to use a well-calibrated GTSM and co-located seismic instrument as a partial ?gradient tensor? seismic instrument that can serve as a ?point? seismic array for analyzing the P-SV wave field. Such an instrument can, in principle, find wave attributes such as propagation azimuth and slowness. The ANZA PBO network is, therefore, an array of point arrays that can be used to study regional wave propagation, wave scattering, and source parameters from moderate events in southern California that should be useful in Earthquake Early Warning. This will be a new application of EarthScope facilities.
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/68039
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Charles Langston.Creating a New Seismic Instrument from EarthScope Strainmeter Installations.2015.