The horizontal velocity field in southern California from a combination of terrestrial and space-geodetic data

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993.Includes bibliographical references (p. 45-48).by Danan Dong.Ph.D

Multiscale estimation of GPS velocity fields

We present a spherical wavelet-based multiscale approach for estimating a spatial velocity field on the sphere from a set of irregularly spaced geodetic displacement observations. Because the adopted spherical wavelets are analytically differentiable, spatial gradient tensor quantities such as dilatation rate, strain rate and rotation rate can be directly computed using the same coefficients. In a series of synthetic and real examples,we illustrate the benefit of themultiscale approach, in particular, the inherent ability of the method to localize a given deformation field in space and scale as well as to detect outliers in the set of observations. This approach has the added benefit of being able to locally match the smallest resolved process to the local spatial density of observations, thereby both maximizing the amount of derived information while also allowing the comparison of derived quantities at the same scale but in different regions.We also consider the vertical component of the velocity field in our synthetic and real examples, showing that in some cases the spatial gradients of the vertical velocity field may constitute a significant part of the deformation. This formulation may be easily applied either regionally or globally and is ideally suited as the spatial parametrization used in any automatic time-dependent geodetic transient detector

Multiscale estimation of GPS velocity fields

We present a spherical wavelet-based multiscale approach for estimating a spatial velocity field on the sphere from a set of irregularly spaced geodetic displacement observations. Because the adopted spherical wavelets are analytically differentiable, spatial gradient tensor quantities such as dilatation rate, strain rate and rotation rate can be directly computed using the same coefficients. In a series of synthetic and real examples,we illustrate the benefit of themultiscale approach, in particular, the inherent ability of the method to localize a given deformation field in space and scale as well as to detect outliers in the set of observations. This approach has the added benefit of being able to locally match the smallest resolved process to the local spatial density of observations, thereby both maximizing the amount of derived information while also allowing the comparison of derived quantities at the same scale but in different regions.We also consider the vertical component of the velocity field in our synthetic and real examples, showing that in some cases the spatial gradients of the vertical velocity field may constitute a significant part of the deformation. This formulation may be easily applied either regionally or globally and is ideally suited as the spatial parametrization used in any automatic time-dependent geodetic transient detector. Key words : Wavelet transform, Satellite geodesy, Seismic cycle, Transient deformation, Kinematics of crustal and mantle deformation.nbsp

Geodetic Strain Analysis Tool

A geodetic software analysis tool enables the user to analyze 2D crustal strain from geodetic ground motion, and create models of crustal deformation using a graphical interface. Users can use any geodetic measurements of ground motion and derive the 2D crustal strain interactively. This software also provides a forward-modeling tool that calculates a geodetic velocity and strain field for a given fault model, and lets the user compare the modeled strain field with the strain field obtained from the user s data. Users may change parameters on-the-fly and obtain a real-time recalculation of the resulting strain field. Four data products are computed: maximum shear, dilatation, shear angle, and principal components. The current view and data dependencies are processed first. The remaining data products and views are then computed in a round-robin fashion to anticipate view changes. When an analysis or display parameter is changed, the affected data products and views are invalidated and progressively re-displayed as available. This software is designed to facilitate the derivation of the strain fields from the GPS and strain meter data that sample it to facilitate the understanding of the strengths and weaknesses of the strain field derivation from continuous GPS (CGPS) and other geodetic data from a variety of tectonic settings, to converge on the "best practices" strain derivation strategy for the Solid Earth Science ESDR System (SESES) project given the CGPS station distribution in the western U.S., and to provide SESES users with a scientific and educational tool to explore the strain field on their own with user-defined parameters

Integration of transient strain events with models of plate coupling and areas of great earthquakes in southwest Japan

We model the crustal deformation caused by two long-term subduction slip transients in southwest Japan, which we refer to as the 2000–2004 Tokai and the 2002–2004 Bungo Channel slow slip events (SSEs). We use re-analysed GEONET position time-series, and a Kalman filter based network inversion method to image the spatiotemporal slip variation of the two events on the plate interface during the period of 1998–2004.67 and 2000–2005. Both events are found to have complex slip histories with multiple subevents. In addition to a newly identified slip subevent in 2002–2003, we find that the major event in the Bungo Channel SSE initiated in early 2003 beneath the northeastern corner of the region and expanded southwestward, in contrast to the slip characteristics suggested by other studies. The re-analysed GPS data in the Tokai region shows a renewed slip activity for the Tokai SSE in early 2003–2004 at a similar location as in the period of 2001–2002. The equivalent M w for both the Tokai and Bungo Channel SSEs are about 7.0. Our results show that the Tokai SSE appears to start before the Miyaki-Kozu seismovolcanic event. Integrating plate coupling and SSEs shows that the transient slip zones are located in a region between the locked zones and the epicentres of the low frequency earthquakes (LFEs). At least part of the interseismic slip deficit is released by episodic SSEs beneath the Bungo Channel region. We find excellent temporal correspondence between transient slip and adjacent LFEs for both SSE, suggesting that they are closely related and possibly reflect that long-term slow slip may modulate the occurrence of LFEs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79234/1/j.1365-246X.2010.04599.x.pd

Estimation of interplate coupling in the Nankai trough, Japan using GPS data from 1996 to 2006

We used three-component surface velocities in southwest Japan to estimate plate coupling on the subducting plate interface at the Nankai trough. We analyzed continuous GPS data from the Japanese GEONET network from 1996 to 2006 using a consistent analysis strategy that generates bias-fixed solutions for the entire network. We applied systematic time-series analysis methods to estimate common mode error, which improved position solutions for the entire network. To allow for differences in regional deformation sources, we modelled the plate coupling on the plate interface beneath Shikoku island to Kii Peninsula and the Tokai-Suruga trough separately. The results show strong coupling at a depth of ∼10–30 km off Shikoku and Kii Peninsula. The spatial variation in plate coupling coincides well with the coseismic rupture zones of the past large earthquakes. Maximum slip deficit rates of ∼2–3 cm yr −1 at the depth of ∼5–25 km are found beneath the Tokai area, consistent with results from other studies. The downdip limits of the highly coupled areas and transition zones beneath Shikoku and the Kii Peninsula correspond approximately to estimates of the 450 °C isotherms. Good correlation is observed between the lateral variations of the slip deficit distribution, low frequency earthquakes, and coseismic slip. This correlation suggests that temperature, and possibly fluid variations, contribute to such correlation in space. The interplate slip deficit derived from the GPS velocities over the 10 yr of observations is generally compatible with the results over shorter time spans, suggesting that plate coupling in SW Japan does not change significantly over the period of these GPS measurements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79077/1/j.1365-246X.2010.04600.x.pd

Non-linearity of geocentre motion and its impact on the origin of the terrestrial reference frame

The terrestrial reference frame is a cornerstone for modern geodesy and its applications for a wide range of Earth sciences. The underlying assumption for establishing a terrestrial reference frame is that the motion of the solid Earth's figure centre relative to the mass centre of the Earth system on a multidecadal timescale is linear. However, past international terrestrial reference frames (ITRFs) showed unexpected accelerated motion in their translation parameters. Based on this underlying assumption, the inconsistency of relative origin motions of the ITRFs has been attributed to data reduction imperfection. We investigated the impact of surface mass loading from atmosphere, ocean, snow, soil moisture, ice sheet, glacier and sea level from 1983 to 2008 on the geocentre variations. The resultant geocentre time-series display notable trend acceleration from 1998 onward, in particular in the z-component. This effect is primarily driven by the hydrological mass redistribution in the continents (soil moisture, snow, ice sheet and glacier). The acceleration is statistically significant at the 99 per cent confidence level as determined using the Mann-Kendall test, and it is highly correlated with the satellite laser ranging determined translation series. Our study, based on independent geophysical and hydrological models, demonstrates that, in addition to systematic errors from analysis procedures, the observed non-linearity of the Earth-system behaviour at interannual timescales is physically driven and is able to explain 42 per cent of the disparity between the origins of ITRF2000 and ITRF2005, as well as the high level of consistency between the ITRF2005 and ITRF2008 origins

Thermoelastic Seasonal Deformation in Chinese Mainland

In this paper, we explore the thermoelastic seasonal deformation in Chinese mainland based on the 260 GPS sites of crustal movement observation network of China (CMONOC). The results show that the change of land surface temperature can induce remarkable surface deformation in China. The most affected site is HLAR in Inner Mongolia, China. Its seasonal amplitude of surface deformation is about~2.293mm. and the site HIYS in Hainan is the least affected. The seasonal amplitude of surface deformation is about~0.177mm. Applying the thermoelastic seasonal deformation information in GRACE data analysis and the Mass loading models (MODEL), refined three-dimensional seasonal deformation map are derived. Taking GPS measurements as references, refined results show that the annual deformation derived from the MODEL and the GRACE data have been improved by about 6%,6%,2%;16%,5%,15% in the east, north and height components respectively