Improved estimation of free oscillation splitting coefficients using a combination of autoregressive estimation and the neighborhood algorithm

GSTDTAP

项目编号	1547234
	Improved estimation of free oscillation splitting coefficients using a combination of autoregressive estimation and the neighborhood algorithm
	T. Guy Masters
主持机构	University of California-San Diego Scripps Inst of Oceanography
项目开始年	2016
	2016
项目结束日期	2017-12-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	78201(USD)
国家	美国
语种	英语
英文摘要	Plate tectonics is the outward expression of the mantle circulation that allows the Earth to get rid of its heat. This convective flow is driven by lateral variations in density induced by changes in temperature and/or composition throughout the mantle. The goal of seismic tomography is to image these lateral variations and it has been quite successful in imaging variations in seismic velocities. Imaging variations in density is much more challenging. One way to do this is to use the splitting and coupling of "free oscillations" of the Earth excited by large earthquakes. Such oscillations are analogous to the tones of a bell after it has been struck. Here the PI proposes a novel way to analyze such oscillations of the Earth that will result in better 3D models of the structure of the mantle and so shed light on the forces driving plate tectonics. The construction of 3D models of the Earth also improves our ability to accurately model the propagation of seismic waves. This has many societal implications including an improved ability to estimate seismic hazard, and to monitor a nuclear test ban treaty. In global seismic tomography, the goal is to image the 3D structure of the Earth in both the mantle and inner core. Currently, images of 3D shear velocity in the mantle are quite robust but images of compressional velocity (or, better yet, bulk sound speed) are less so, and images of 3D density structure still remain controversial. One thing that is clear though is that there is no simple scaling between these parameters in the mantle implying laterally and depth varying causes of the observed anomalies. 3D density structure is not only important for discriminating between possible physical causes of anomalies inside the Earth, but it is this that drives convective flow and so has consequences for determining dynamic topography and the geoid. One of the few ways to get at 3D density structure from a seismic point of view is through the study of free-oscillation splitting and coupling. Here the PI team proposes a modification to the autoregressive technique (AR) by combining it with the Neighborhood Algorithm (NA). The main advantage of the resulting algorithm is that it is not sensitive to the source (which can often be complicated for the large events used in free-oscillation work) but allows direct control over the form of solution so that its robustness can be assessed. The method will be applied to an expanded dataset of 3-component recordings from all major earthquakes in the last 20+ years to study both (effectively) uncoupled multiplets and coupled multiplets so giving constraints on both odd and even structure. The free oscillation structure coefficients so determined will be combined with other types of seismic data to give a more reliable determination of the long-wavelength 3D density structure in the Earth, as well as significantly improving our knowledge of long-wavelength elastic and anelastic structure throughout the Earth.
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/69049
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	T. Guy Masters.Improved estimation of free oscillation splitting coefficients using a combination of autoregressive estimation and the neighborhood algorithm.2016.