scholarly journals Post-critical SsPmp and its applications to Virtual Deep Seismic Sounding (VDSS) – 2: 1-D imaging of the crust/mantle and joint constraints with receiver functions

2019 ◽  
Vol 219 (2) ◽  
pp. 1334-1347 ◽  
Author(s):  
Tianze Liu ◽  
Simon L Klemperer ◽  
Gabriel Ferragut ◽  
Chunquan Yu
Keyword(s):  
Upper Mantle ◽  
Receiver Functions ◽  
Deep Seismic Sounding ◽  
Moho Depth ◽  
Joint Analysis ◽  
Crust And Upper Mantle ◽  
Slave Craton ◽  
Single Station ◽  
Seismic Sounding ◽  
Novel Method

SUMMARY Virtual Deep Seismic Sounding (VDSS) has emerged as a novel method to image the crust–mantle boundary (CMB) and potentially other lithospheric boundaries. In Part 1, we showed that the arrival time and waveform of post-critical SsPmp, the post-critical reflection phase at the CMB used in VDSS, is sensitive to several different attributes of the crust and upper mantle. Here, we synthesize our methodology of deriving Moho depth, average crustal Vp and uppermost-mantle Vp from single-station observations of post-critical SsPmp under a 1-D assumption. We first verify our method with synthetics and then substantiate it with a case study using the Yellowknife and POLARIS arrays in the Slave Craton, Canada. We show good agreement of crustal and upper-mantle properties derived with VDSS with those given by previous active-source experiments and our own P receiver functions (PRF) in our study area. Finally, we propose a PRF-VDSS joint analysis method to constrain average crustal Vp/Vs ratio and composition. Our PRF-VDSS joint analysis shows that the southwest Slave Craton has an intermediate crustal composition, most consistent with a Mesoarchean age.

Post-critical SsPmp and its applications to virtual deep seismic sounding (VDSS)—3: back-projection imaging of the crust–mantle boundary in a heterogeneous lithosphere, theory and application

2020 ◽  
Vol 223 (3) ◽  
pp. 2166-2187
Author(s):  
Tianze Liu ◽  
Simon L Klemperer ◽  
Chunquan Yu ◽  
Jieyuan Ning
Keyword(s):  
Projection Method ◽  
Receiver Functions ◽  
Deep Seismic Sounding ◽  
Moho Depth ◽  
Lithospheric Structure ◽  
Ray Theory ◽  
Back Projection ◽  
Mantle Boundary ◽  
Seismic Sounding ◽  
Lateral Variations

SUMMARY Virtual deep seismic sounding (VDSS) uses the arrival time of post-critical SsPmp relative to the direct S wave to infer Moho depth at the Pmp reflection point. Due to the large offset between the virtual source and the receiver, SsPmp is more sensitive to lateral variations of structures than near-vertical phases such as Ps, which is used to construct conventional P receiver functions. However, the way post-critical SsPmp is affected by lateral variations in lithospheric structure is not well understood, and previous studies largely assumed a 1-D structure when analysing SsPmp waveforms. Here we present synthetic tests with various 2-D models to show that lateral variations in lithospheric structures, from the lithosphere–asthenosphere boundary (LAB) to sedimentary basins, profoundly affect traveltime, phase and amplitude of post-critical SsPmp, and that a 1-D approximation is usually inappropriate when analysing 2-D data. Despite these strong effects we show, with synthetic examples and the ChinArray data from the Ordos Block in northern China, that a simple ray-theory-based back-projection method can retrieve the geometry of the crust–mantle boundary (CMB) given array observations in cases with moderate lateral variations in the CMB and/or the LAB. The success of our back-projection method indicates that ray-theory approximations are sufficient in modelling SsPmp traveltimes in the presence of moderate lateral heterogeneity. In contrast, we show that the ray theory is generally insufficient in modelling SsPmp phase shifts in a strongly heterogeneous lithosphere due to non-planar downgoing P waves incident at the CMB. Nonetheless, our results demonstrate the feasibility of direct imaging of the CMB with post-critical SsPmp even in the presence of 2-D variations of lithospheric structure.

Constraints on the composition of the crust and uppermost mantle in northwestern Canada: Vp/Vs variations along Lithoprobe's SNorCLE transect

2005 ◽  
Vol 42 (6) ◽  
pp. 1205-1222 ◽  
Author(s):  
Gabriela Fernández-Viejo ◽  
Ron M Clowes ◽  
J Kim Welford
Keyword(s):  
Wave Velocity ◽  
Upper Mantle ◽  
Laboratory Data ◽  
High Ratio ◽  
P Wave ◽  
S Wave ◽  
Uppermost Mantle ◽  
Crust And Upper Mantle ◽  
Slave Craton ◽  
Crustal Composition

Shear-wave seismic data recorded along four profiles during the SNoRE 97 (1997 Slave – Northern Cordillera Refraction Experiment) refraction – wide-angle reflection experiment in northwestern Canada are analyzed to provide S-wave velocity (Vs) models. These are combined with previous P-wave velocity (Vp) models to produce cross sections of the ratio Vp/Vs for the crust and upper mantle. The Vp/Vs values are related to rock types through comparisons with published laboratory data. The Slave craton has low Vp/Vs values of 1.68–1.72, indicating a predominantly silicic crustal composition. Higher values (1.78) for the Great Bear and eastern Hottah domains of the Wopmay orogen imply a more mafic than average crustal composition. In the western Hottah and Fort Simpson arc, values of Vp/Vs drop to ∼1.69. These low values continue westward for 700 km into the Foreland and Omineca belts of the Cordillera, providing support for the interpretation from coincident seismic reflection studies that much of the crust from east of the Cordilleran deformation front to the Stikinia terrane of the Intermontane Belt consists of quartzose metasedimentary rocks. Stikinia shows values of 1.78–1.73, consistent with its derivation as a volcanic arc terrane. Upper mantle velocity and ratio values beneath the Slave craton indicate an ultramafic peridotitic composition. In the Wopmay orogen, the presence of low Vp/Vs ratios beneath the Hottah – Fort Simpson transition indicates the presence of pyroxenite in the upper mantle. Across the northern Cordillera, low Vp values and a moderate-to-high ratio in the uppermost mantle are consistent with the region's high heat flow and the possible presence of partial melt.

A crust and upper mantle model for Novaya Zemlya from Rayleigh-wave dispersion data

1978 ◽  
Vol 68 (6) ◽  
pp. 1651-1662
Author(s):  
Douglas W. McCowan ◽  
Peter Glover ◽  
Shelton S. Alexander
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Upper Mantle ◽  
Wave Dispersion ◽  
Surface Wave Dispersion ◽  
Crust And Upper Mantle ◽  
Novaya Zemlya ◽  
Phase Velocity Dispersion ◽  
Single Station

abstract We derive a shear-wave crust and upper mantle structure for the southern part of Novaya Zemlya by an application of the two-event, single-station method of Rayleigh-wave phase-velocity dispersion analysis. This method provides a means of isolating the surface-wave dispersion characteristics of a remote source region using only teleseismic recordings. The observed phase-velocity data are then systematically inverted to obtain a best-fitting model. Our preferred model has a 45-km thick crust with no shear-wave low-velocity zone in the upper mantle. It is similar to published structures for the southern Ural mountains and is therefore compatible with the premise that Novaya Zemlya is a nothern extension of the Urals.

scholarly journals Crustal and upper mantle structure in the Ryukyu Island Arc deduced from deep seismic sounding

1990 ◽  
Vol 102 (3) ◽  
pp. 631-651 ◽  
Author(s):  
T. Iwasaki ◽  
N. Hirata ◽  
T. Kanazawa ◽  
J. Melles ◽  
K. Suyehiro ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Island Arc ◽  
Deep Seismic Sounding ◽  
Ryukyu Island ◽  
Mantle Structure ◽  
Upper Mantle Structure ◽  
Seismic Sounding
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