I. A seismotectonic study of the Middle America Subduction Zone. II. Lithosphere and upper mantle structure of the Canadian Shield and Eastern North America

This thesis consists of two separate parts. Part I (Chapter 1) is concerned with seismotectonics of the Middle America subduction zone. In this chapter, stress distribution and Benioff zone geometry are investigated along almost 2000 km of this subduction zone, from the Rivera Fracture Zone in the north to Guatemala in the south. Particular emphasis is placed on the effects on stress distribution of two aseismic ridges, the Tehuantepec Ridge and the Orozco Fracture Zone, which subduct at seismic gaps. Stress distribution is determined by studying seismicity distribution, and by analysis of 190 focal mechanisms, both new and previously published, which are collected here. In addition, two recent large earthquakes that have occurred near the Tehuantepec Ridge and the Orozco Fracture Zone are discussed in more detail. A consistent stress release pattern is found along most of the Middle America subduction zone: thrust events at shallow depths, followed down-dip by an area of low seismic activity, followed by a zone of normal events at over 175 km from the trench and 60 km depth. The zone of low activity is interpreted as showing decoupling of the plates, and the zone of normal activity as showing the breakup of the descending plate. The portion of subducted lithosphere containing the Orozco Fracture Zone does not differ significantly, in Benioff zone geometry or in stress distribution, from adjoining segments. The Playa Azul earthquake of October 25, 1981, M_s=7.3, occurred in this area. Body and surface wave analysis of this event shows a simple source with a shallow thrust mechanism and gives M_o=1.3x10²⁷ dyne-cm. A stress drop of about 45 bars is calculated; this is slightly higher than that of other thrust events in this subduction zone. In the Tehuantepec Ridge area, only minor differences in stress distribution are seen relative to adjoining segments. For both ridges, the only major difference from adjoining areas is the infrequency or lack of occurrence of large interplate thrust events.

Part II involves upper mantle P wave structure studies, for the Canadian shield and eastern North America. In Chapter 2, the P wave structure of the Canadian shield is determined through forward waveform modeling of the phases P_nl, P, and PP. Effects of lateral heterogeneity are kept to a minimum by using earthquakes just outside the shield as sources, with propagation paths largely within the shield. Previous mantle structure studies have used recordings of P waves in the upper mantle triplication range of 15-30°; however, the lack of large earthquakes in the shield region makes compilation of a complete P wave dataset difficult. By using the phase PP, which undergoes triplications at 30-60°, much more information becomes available. The WKBJ technique is used to calculate synthetic seismograms for PP, and these records are modeled almost as well as the P. A new velocity model, designated S25, is proposed for the Canadian shield. This model contains a thick, high-Q, high-velocity lid to 165 km and a deep low-velocity zone. These features combine to produce seismograms that are markedly different from those generated by other shield structure models. The upper mantle discontinuities in S25 are placed at 405 and 660 km, with a simple linear gradient in velocity between them. Details of the shape of the discontinuities are not well constrained. Below 405 km, this model is not very different from many proposed P wave models for both shield and tectonic regions.

Chapter 3 looks in more detail at recordings of P_nl in eastern North America. First, seismograms from four eastern North American earthquakes are analyzed, and seismic moments for the events are calculated. These earthquakes are important in that they are among the largest to have occurred in eastern North America in the last thirty years, yet in some cases were not large enough to produce many good long-period teleseismic records. A simple layer-over-a-halfspace model is used for the initial modeling, and is found to provide an excellent fit for many features of the observed waveforms. The effects on P_nl of varying lid structure are then investigated. A thick lid with a positive gradient in velocity, such as that proposed for the Canadian shield in Chapter 2, will have a pronounced effect on the waveforms, beginning at distances of 800 or 900 km. P_nl records from the same eastern North American events are recalculated for several lid structure models, to survey what kinds of variations might be seen. For several records it is possible to see likely effects of lid structure in the data. However, the dataset is too sparse to make any general observations about variations in lid structure. This type of modeling is expected to be important in the future, as the analysis is extended to more recent eastern North American events, and as broadband instruments make more high-quality regional recordings available.

The Dubawnt Lake palaeo-ice stream: evidence for dynamic ics sheet behaviour on the Canadian Shield and insights regarding the controls on ice-stream location and vigour

We report evidence for a major ice stream that operated over the northwestern Canadian Shield in the Keewatin Sector of the Laurentide Ice Sheet during the last deglaciation 9000-8200 (uncalibrated) yr BP. It is reconstructed at 450 km in length, 140 km in width, and had an estimated catchment area of 190000 km. Mapping from satellite imagery reveals a suite of bedforms ('flow-set') characterized by a highly convergent onset zone, abrupt lateral margins, and where flow was presumed to have been fastest, a remarkably coherent pattern of mega-scale glacial lineations with lengths approaching 13 km and elongation ratios in excess of 40:1. Spatial variations in bedform elongation within the flow-set match the expected velocity field of a terrestrial ice stream. The flow pattern does not appear to be steered by topography and its location on the hard bedrock of the Canadian Shield is surprising. A soft sedimentary basin may have influenced ice-stream activity by lubricating the bed over the downstream crystalline bedrock, but it is unlikely that it operated over a pervasively deforming till layer. The location of the ice stream challenges the view that they only arise in deep bedrock troughs or over thick deposits of 'soft' fine-grained sediments. We speculate that fast ice flow may have been triggered when a steep ice sheet surface gradient with high driving stresses contacted a proglacial lake. An increase in velocity through calving could have propagated fast ice flow upstream (in the vicinity of the Keewatin Ice Divide) through a series of thermomechanical feedback mechanisms. It exerted a considerable impact on the Laurentide Ice Sheet, forcing the demise of one of the last major ice centres.

Laurentide ice streaming on the Canadian Shield: A conflict with the soft-bedded ice stream paradigm?

Elucidating the controls on the location and vigor of ice streams is crucial to understanding the processes that lead to fast disintegration of ice flows and ice sheets. In the former North American Laurentide ice sheet, ice stream occurrence appears to have been governed by topographic troughs or areas of soft-sediment geology. This paper reports robust evidence of a major paleo-ice stream over the northwestern Canadian Shield, an area previously assumed to be incompatible with fast ice flow because of the low relief and relatively hard bedrock. A coherent pattern of subglacial bedforms (drumlins and megascalle glacial lineations) demarcates the ice stream flow set, which exhibits a convergent onset zone, a narrow main trunk with abrupt lateral margins, and a lobate terminus. Variations in bedform elongation ratio within the flow set match theoretical expectations of ice velocity. In the center of the ice stream, extremely parallel megascalle glacial lineations tens of kilometers long with elongation ratios in excess of 40:1 attest to a single episode of rapid ice flow. We conclude that while bed properties are likely to be influential in determining the occurrence and vigor of ice streams, contrary to established views, widespread soft-bed geology is not an essential requirement for those ice streams without topographic control. We speculate that the ice stream acted as a release valve on ice-sheet mass balance and was initiated by the presence of a proglacial lake that destabilized the ice-sheet margin and propagated fast ice flow through a series of thermomechanical feedbacks involving ice flow and temperature.

Evolution of late glacial ice-marginal lakes on the northwestern Canadian Shield and their influence on the location of the Dubawnt Lake palaeo-ice stream

During deglaciation of the North American Laurentide Ice Sheet large proglacial lakes developed in positions where proglacial drainage was impeded by the ice margin. For some of these lakes, it is known that subsequent drainage had an abrupt and widespread impact on North Atlantic Ocean circulation and climate, but less is known about the impact that the lakes exerted on ice sheet dynamics. This paper reports palaeogeographic reconstructions of the evolution of proglacial lakes during deglaciation across the northwestern Canadian Shield, covering an area in excess of 1,000,000 km(2) as the ice sheet retreated some 600 km. The interactions between proglacial lakes and ice sheet flow are explored, with a particular emphasis on whether the disposition of lakes may have influenced the location of the Dubawnt Lake ice stream. This ice stream falls outside the existing paradigm for ice streams in the Laurentide Ice Sheet because it did not operate over fined-grained till or lie in a topographic trough. Ice margin positions and a digital elevation model are utilised to predict the geometry and depth of proglacial takes impounded at the margin at 30-km increments during deglaciation. Palaeogeographic reconstructions match well with previous independent estimates of lake coverage inferred from field evidence, and results suggest that the development of a deep lake in the Thelon drainage basin may have been influential in initiating the ice stream by inducing calving, drawing down ice and triggering fast ice flow. This is the only location alongside this sector of the ice sheet where large (>3000 km(2)), deep lakes (similar to120 m) are impounded for a significant length of time and exactly matches the location of the ice stream. It is speculated that the commencement of calving at the ice sheet margin may have taken the system beyond a threshold and was sufficient to trigger rapid motion but that once initiated, calving processes and losses were insignificant to the functioning of the ice stream. It is thus concluded that proglacial lakes are likely to have been an important control on ice sheet dynamics during deglaciation of the Laurentide Ice Sheet. (C) 2004 Elsevier B.V. All rights reserved.

ROCK OUTCROPS IN THE CANADIAN SHIELD: AN INVESTIGATION OF CONTAMINANT TRANSPORT FROM SURFACE SOURCES IN FRACTURED ROCK AQUIFERS

Flow, recharge and transport dynamics in fractured rock aquifers with low lying rock outcrops is a largely unexplored area of study in hydrogeology. The purpose of this thesis is to examine these topics in an agricultural area in Eastern Ontario. The study consists of a regional scale groundwater quality study, an infiltration experiment that considers bacteria transport from the ground surface to a well, and a numerical modelling study that tests the parameters that affect surface infiltration of a tracer from a rock outcrop to a deeper horizontal fracture. In the water quality study, approximately 65% of the samples contained total coliform, 16% contained E. coli, and 1% contained nitrate-N at greater than 5 mg/L. Occurrence of E. coli increased when considering seasonality, where wells were drilled on rock outcrops, and for shallow well intervals. Nitrate-N did not occur above the Guidelines for Canadian Drinking Water Quality (Health Canada, 2012) of 10 mg/L. Rapid arrival times were observed in the infiltration study for both the microspheres (30 minutes) and a dye tracer (45 minutes) in a well approximately 6.0 m in horizontal and 2.8 m in vertical distance from the tracer source. Transport velocities were approximately 38.9 m/day for the dye tracer and 115.2 m/day for the colloidal tracer. Results of the model runs indicate that overburden can provide an effective protective layer to transport in fractures, that high groundwater velocities occur in larger fracture apertures and higher gradients dilute tracer concentrations, and that lower groundwater velocities occur with smaller fracture apertures and lower gradients result in elevated tracer concentrations. Lower rainfall rates, larger fracture apertures, early tracer time, larger gradients, and lower water levels maintained unsaturated conditions for longer time periods such that tracer transport was delayed until saturated conditions were attained. The overall heterogeneity of this aquifer environment creates a source water protection conundrum where the water quality is generally good, while transport can occur very quickly in proximity to rock outcrops and in areas with limited overburden.

CAN-HK : An a priori crustal model for the Canadian Shield

Peer reviewed

CAN-HK : An a priori crustal model for the Canadian Shield

Peer reviewed

CAN-HK : An a priori crustal model for the Canadian Shield

Peer reviewed

ROCK OUTCROPS IN THE CANADIAN SHIELD: AN INVESTIGATION OF CONTAMINANT TRANSPORT FROM SURFACE SOURCES IN FRACTURED ROCK AQUIFERS

Flow, recharge and transport dynamics in fractured rock aquifers with low lying rock outcrops is a largely unexplored area of study in hydrogeology. The purpose of this thesis is to examine these topics in an agricultural area in Eastern Ontario. The study consists of a regional scale groundwater quality study, an infiltration experiment that considers bacteria transport from the ground surface to a well, and a numerical modelling study that tests the parameters that affect surface infiltration of a tracer from a rock outcrop to a deeper horizontal fracture. In the water quality study, approximately 65% of the samples contained total coliform, 16% contained E. coli, and 1% contained nitrate-N at greater than 5 mg/L. Occurrence of E. coli increased when considering seasonality, where wells were drilled on rock outcrops, and for shallow well intervals. Nitrate-N did not occur above the Guidelines for Canadian Drinking Water Quality (Health Canada, 2012) of 10 mg/L. Rapid arrival times were observed in the infiltration study for both the microspheres (30 minutes) and a dye tracer (45 minutes) in a well approximately 6.0 m in horizontal and 2.8 m in vertical distance from the tracer source. Transport velocities were approximately 38.9 m/day for the dye tracer and 115.2 m/day for the colloidal tracer. Results of the model runs indicate that overburden can provide an effective protective layer to transport in fractures, that high groundwater velocities occur in larger fracture apertures and higher gradients dilute tracer concentrations, and that lower groundwater velocities occur with smaller fracture apertures and lower gradients result in elevated tracer concentrations. Lower rainfall rates, larger fracture apertures, early tracer time, larger gradients, and lower water levels maintained unsaturated conditions for longer time periods such that tracer transport was delayed until saturated conditions were attained. The overall heterogeneity of this aquifer environment creates a source water protection conundrum where the water quality is generally good, while transport can occur very quickly in proximity to rock outcrops and in areas with limited overburden.

The effects of the non-native invertebrate predator Bythotrephes longimanus and declining aqueous calcium on crustacean zooplankton communities in Canadian Shield lakes

Over the last several decades, human activities have resulted in environmental changes that have increased the number of stressors that can act on a single environment. In Canadian Shield lakes, two recent stressors, the invasion of Bythotrephes longimanus and calcium decline, have been documented. Widespread acidification of hundreds of North American lakes has resulted in the precipitous decline of lake water calcium concentration. Crustacean zooplankton with high calcium demands are likely to be vulnerable to calcium decline, especially <1.5 mg Ca/L, where survival and reproduction rates are reduced. These taxa are also vulnerable to predation by Bythotrephes that has been implicated in the loss of pelagic biodiversity in soft water lakes. Despite laboratory and field studies aimed at understanding the independent impact of these stressors, it is unclear how their co-occurrence will influence community response. Using a combination of data from a large regional lake survey and field experiments, I examined the individual and joint effects of Bythotrephes and calcium decline on native zooplankton community structure. Results demonstrated that much is known about Bythotrephes and our findings of reduced total zooplankton and species richness, due to the loss of Cladocera, are consistent with field surveys and other experimental studies. While we did not detect strong evidence for an effect of calcium on zooplankton using the lowest calcium concentration among invaded lakes (1.2 mg Ca/L), there is evidence that, as lake water calcium concentrations fall <1 mg Ca/L, per capita growth rates of a broad variety of taxa are expected to decline. At the regional scale, negative effects of Bythotrephes and calcium on abundances of small cladocerans and Daphnia pulicaria, respectively, were in agreement with my experimental observations. We also observed significant interactions between Bythotrephes and calcium for a broad variety of taxa. As Bythotrephes continues to spread and invade lakes that are also declining in aqueous calcium, both stressors are likely to amplify negative effects on Cladocera that appear the most vulnerable. Loss of these important zooplankton in response to both Bythotrephes and calcium decline, is likely to lower zooplankton productivity, with potential effects on phytoplankton and higher trophic levels.

Petrology and textural classification of the Jericho kimberlite, northern Slave Province, Nunavut, Canada

The paper presents data on petrology, bulk rock and mineral compositions, and textural classification of the Middle Jurassic Jericho kimberlite (Slave craton, Canada). The kimberlite was emplaced as three steep-sided pipes in granite that was overlain by limestones and minor soft sediments. The pipes are infilled with hypabyssal and pyroclastic kimberlites and connected to a satellite pipe by a dyke. The Jericho kimberlite is classified as a Group Ia, lacking groundmass tetraferriphlogopite and containing monticellite pseudomorphs. The kimberlite formed, during several consecutive emplacement events of compositionally different batches of kimberlite magma. Core-logging and thin-section observations identified at least two phases of hypabyssal kimberlites and three phases of pyroclastic kimberlites. Hypabyssal kimberlites intruded as a main dyke (HK1) and as late small-volume aphanitic and vesicular dykes. Massive pyroclastic kimberlite (MPK1) predominantly filled the northern and southern lobes of the pipe and formed from magma different from the HK1 magma. The MPK1 magma crystallized Ti-, Fe-, and Cr-rich phlogopite without rims of barian phlogopite, and clinopyroxene and spinel without atoll structures. MPK1 textures, superficially reminiscent of tuffisitic kimberlite, are caused by pervasive contamination by granite xenoliths. The next explosive events filled the central lobe with two varieties of pyroclastic kimberlite: (1) massive and (2) weakly bedded, normally graded pyroclastic kimberlite. The geology of the Jericho pipe differs from the geology of South African or the Prairie kimberlites, but may resemble Lac de Gras pipes, in which deeper erosion removed upper fades of resedimented kimberlites.

Difficulties in distinguishing coherent from fragmental kimberlite: A case study of the Muskox pipe (Northern Slave Province, Nunavut, Canada)

Kimberlite drill core from the Muskox pipe (Northern Slave Province, Nunavut, Canada) highlights the difficulties in distinguishing coherent from fragmental kimberlite and assessing the volcanological implications of the apparent gradational contact between the two facies. Using field log data, petrography, and several methods to quantify crystal and xenolith sizes and abundances, the pipe is divided into two main facies, dark-coloured massive kimberlite (DMK) and light-coloured fragmental kimberlite (LFK). DMK is massive and homogeneous, containing country-rock lithic clasts (~ 10%) and olivine macrocrysts (~ 15%) set in a dark, typically well crystallised, interstitial medium containing abundant microphenocrysts of olivine (~ 15%), opaques and locally monticellite, all of which are enclosed by mostly serpentine. In general, LFK is also massive and structureless, containing ~ 20% country-rock lithic clasts and ~ 12% olivine macrocrysts. These framework components are supported in a matrix of serpentinized olivine microphenocrysts (10%), microlites of clinopyroxene, and phlogopite, all of which are enclosed by serpentine. The contact between DMK and LFK facies is rarely sharp, and more commonly is gradational (from 5 cm to ~ 10 m). The contact divides the pipe roughly in half and is sub-vertical with an irregular shape, locally placing DMK facies both above and below the fragmental rocks. Most features of DMK are consistent with a fragmental origin, particularly the crystal- and xenolith-rich nature (~ 55-65%), but there are some similarities with rocks described as coherent kimberlite in the literature. We discuss possible origins of gradational contacts and consider the significance for understanding the origin of the DMK facies, with an emphasis on the complications of alteration overprinting of primary textures.

Regional variations in upper mantle structure beneath North America

Several types of seismological data, including surface wave group and phase velocities, travel times from large explosions, and teleseismic travel time anomalies, have indicated that there are significant regional variations in the upper few hundred kilometers of the mantle beneath continental areas. Body wave travel times and amplitudes from large chemical and nuclear explosions are used in this study to delineate the details of these variations beneath North America.

As a preliminary step in this study, theoretical P wave travel times, apparent velocities, and amplitudes have been calculated for a number of proposed upper mantle models, those of Gutenberg, Jeffreys, Lehman, and Lukk and Nersesov. These quantities have been calculated for both P and S waves for model CIT11GB, which is derived from surface wave dispersion data. First arrival times for all the models except that of Lukk and Nersesov are in close agreement, but the travel time curves for later arrivals are both qualitatively and quantitatively very different. For model CIT11GB, there are two large, overlapping regions of triplication of the travel time curve, produced by regions of rapid velocity increase near depths of 400 and 600 km. Throughout the distance range from 10 to 40 degrees, the later arrivals produced by these discontinuities have larger amplitudes than the first arrivals. The amplitudes of body waves, in fact, are extremely sensitive to small variations in the velocity structure, and provide a powerful tool for studying structural details.

Most of eastern North America, including the Canadian Shield has a Pn velocity of about 8.1 km/sec, with a nearly abrupt increase in compressional velocity by ~ 0.3 km/sec near at a depth varying regionally between 60 and 90 km. Variations in the structure of this part of the mantle are significant even within the Canadian Shield. The low-velocity zone is a minor feature in eastern North America and is subject to pronounced regional variations. It is 30 to 50 km thick, and occurs somewhere in the depth range from 80 to 160 km. The velocity decrease is less than 0.2 km/sec.

Consideration of the absolute amplitudes indicates that the attenuation due to anelasticity is negligible for 2 hz waves in the upper 200 km along the southeastern and southwestern margins of the Canadian Shield. For compressional waves the average Q for this region is > 3000. The amplitudes also indicate that the velocity gradient is at least 2 x 10^-3 both above and below the low-velocity zone, implying that the temperature gradient is < 4.8°C/km if the regions are chemically homogeneous.

In western North America, the low-velocity zone is a pronounced feature, extending to the base of the crust and having minimum velocities of 7.7 to 7.8 km/sec. Beneath the Colorado Plateau and Southern Rocky Mountains provinces, there is a rapid velocity increase of about 0.3 km/sec, similar to that observed in eastern North America, but near a depth of 100 km.

Complicated travel time curves observed on profiles with stations in both eastern and western North America can be explained in detail by a model taking into account the lateral variations in the structure of the low-velocity zone. These variations involve primarily the velocity within the zone and the depth to the top of the zone; the depth to the bottom is, for both regions, between 140 and 160 km.

The depth to the transition zone near 400 km also varies regionally, by about 30-40 km. These differences imply variations of 250 °C in the temperature or 6 % in the iron content of the mantle, if the phase transformation of olivine to the spinel structure is assumed responsible. The structural variations at this depth are not correlated with those at shallower depths, and follow no obvious simple pattern.

The computer programs used in this study are described in the Appendices. The program TTINV (Appendix IV) fits spherically symmetric earth models to observed travel time data. The method, described in Appendix III, resembles conventional least-square fitting, using partial derivatives of the travel time with respect to the model parameters to perturb an initial model. The usual ill-conditioned nature of least-squares techniques is avoided by a technique which minimizes both the travel time residuals and the model perturbations.

Spherically symmetric earth models, however, have been found inadequate to explain most of the observed travel times in this study. TVT4, a computer program that performs ray theory calculations for a laterally inhomogeneous earth model, is described in Appendix II. Appendix I gives a derivation of seismic ray theory for an arbitrarily inhomogeneous earth model.

Spatial variability in water quality and surface sediment diatom assemblages in a complex lake basin,lake of the woods,ontario,canada

Lake of the Woods (LOW) is an international waterbody spanning the Canadian provinces of Ontario and Manitoba, and the U.S. state of Minnesota. In recent years, there has been a perception that water quality has deteriorated in northern regions of the lake, with all increase in the frequency and intensity of toxin-producing cyanobacterial blooms. However, given the lack of long-term data these trends are difficult to verify. As a first step, we examine spatial and seasonal patterns in water quality in this highly complex lake on the Canadian Shield. Further, we examine surface sediment diatom assemblages across multiple sites to determine if they track within-take differences in environmental conditions. Our results show that there are significant spatial patterns in water quality in LOW. Principal Component Analysis divides the lake into three geographic zones based primarily on algal nutrients (i.e., total phosphorus, TP), with the highest concentrations at sites proximal to Rainy River. This variation is closely tracked by sedimentary diatom assemblages, with [TP] explaining 43% of the variation in diatom assemblages across sites. The close correlation between water quality and the surface sediment diatom record indicate that paleoecological models could be used to provide data on the relative importance of natural and anthropogenic sources of nutrients to the lake.

青藏高原东部电性结构特征及地球动力学意义

As the largest and highest plateau on the Earth, the Tibetan Plateau has been a key location for understanding the processes of mountain building and plateau formation during India-Asia continent-continent collision. As the front-end of the collision, the geological structure of eastern Tibetan Plateau is very complex. It is ideal as a natural laboratory for investigating the formation and evolution of the Tibetan Plateau. Institute of Geophysics, Chinese Academy of Sciences (CAS) carried out MT survey from XiaZayii to Qingshuihe in the east part of the plateau in 1998. After error analysis and distortion analysis, the Non-linear Conjugate Gradient inversion(NLCG), Rapid Relaxation Inversin (RRI) and 2D OCCAM Inversion algorithms were used to invert the data. The three models obtained from 3 algorithms provided similar electrical structure and the NLCG model fit the observed data better than the other two models. According to the analysis of skin depth, the exploration depth of MT in Tibet is much more shallow than in stable continent. For example, the Schmucker depth at period 100s is less than 50km in Tibet, but more than 100km in Canadian Shield. There is a high conductivity layer at the depth of several kilometers beneath middle Qiangtang terrane, and almost 30 kilometers beneath northern Qiangtang terrane. The sensitivity analysis of the data predicates that the depth and resistivity of the crustal high conductivity layer are reliable. The MT results provide a high conductivity layer at 20~40km depth, where the seismic data show a low velocity zone. The experiments show that the rock will dehydrate and partially melt in the relative temperature and pressure. Fluids originated from dehydration and partial melting will seriously change rheological characteristics of rock. Therefore, This layer with low velocity and high conductivity layer in the crust is a weak layer. There is a low velocity path at the depth of 90-110 km beneath southeastern Tibetan Plateau and adjacent areas from seismology results. The analysis on the temperature and rheological property of the lithosphere show that the low velocity path is also weak. GPS measurements and the numerical simulation of the crust-mantle deformation show that the movement rate is different for different terranes. The regional strike derived from decomposition analysis for different frequency band and seismic anisotropy indicate that the crust and upper mantle move separately instead of as a whole. There are material flow in the eastern and southeastern Tibetan Plateau. Therefore, the faults, the crustal and upper mantle weak layers are three different boundaries for relatively movement. Those results support the "two layer wedge plates" geodynamic model on Tibetan formation and evolution.