High-Resolution Ps Receiver Function Imaging of the Crust and Mantle Lithosphere Beneath Southern New England and Tectonic Implications

Southern New England exhibits diverse geologic features resulting from past tectonic events. These include Proterozoic and early Paleozoic Laurentian units in the west, several Gondwana-derived terranes that accreted during the Paleozoic in the east, and the Mesozoic Hartford Basin in the central part of the region. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) project involved the deployment of a dense array of 15 broadband seismometers across northern Connecticut to investigate the architecture of lithospheric structures beneath this region and interpret how they were created and modified by past tectonic events in the context of surface geology. We carried out P-to-S receiver function analysis on SEISConn data, including both single-station analysis and common conversion point (CCP) stacking. Our images show that the westernmost part of Connecticut has a much deeper Moho than central and eastern Connecticut. The lateral transition is a well-defined, ∼15 km step-like offset of the Moho over a ∼20 km horizontal distance. The Moho step appears near the surface boundary between the Laurentian margin and the Gondwana-derived Moretown terrane. Possible models for its formation include Ordovician underthrusting of Laurentia and/or modification by younger tectonic events. Other prominent features include a strong positive velocity gradient (PVG) beneath the Hartford basin corresponding to the bottom of the sedimentary units, several west-dipping PVGs in the crust and mantle lithosphere that may correspond to relict slabs or shear zones from past subduction episodes, and a negative velocity gradient (NVG) that may correspond to the base of the lithosphere.publishedVersio

CMT3D - Software

For the modified version of specfem3d_globe, we removed all unnecessary, such as unrelated data, examples, utilities notes, etc. as well as git history. For the model GLAD-M25 please refer to Lei et. al (2020).Software packages to invert for Global Centroid Moment Tensors (GCMT). The software is written in Python and fully modular. Especially the forward modelling method can easily be changed. The software was written with the goal in mind to use the global, seismic forward-modelling software SPECFEM3D_GLOBE to compute three-dimensional, heterogeneous Green's functions for the inversion of the moment tensor.Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility, contract DE-AC05-00OR22725; NSF grant 1644826GCMT3D-SOFTWAREreadme.txt; lwsspy.gcmt3d.tar.gz; source-inversion.tar.gz; lwsspy.tar.gz; lwsspy.seismo.tar.gz; specfem3d_globe.tar.g

CMT3D - Catalog

Catalog of Global CMTSOLUTIONs inverted using 3D Green functions that were computed with the adjoint tomography model GLAD-M25. The full methodology of the inversion procedure is described in the accompanying journal article of the same name.Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility, contract DE-AC05-00OR22725; NSF grant 1644826CMT3D-CATALOGreadme.txt; gcmt3d_dir.tar.gz; gcmt3d.txt

Global Common Conversion Point Stacking and its Applications

Imaging of globally varying subsurface structures is traditionally done by using seismic tomography to map large volumetric anomalies. Methods that image sharp discontinuities in seismic impedance have been restricted to regional or local studies. A global, three-dimensional method is developed that stacks converted earthquake waves originating in such discontinuities, as a function of their conversion points. The method relies on the database GLImER, which contains a global dataset of earthquake recordings that were processed into records of seismic impedance contrasts, namely receiver functions. The implementation of the method follows four steps that are (1) tracing the theoretical conversion points of the receiver functions, (2) creating a global bin grid, (3) binning the receiver functions as a function of their theoretical conversion points, and (4) traveltime-correcting and stacking the binned receiver functions. The stacks are computed with phase-weights to efficiently attenuate incoherencies in the signal. Furthermore, our method takes advantage of the crustal multiples to further enhance the stacks. We test our developed method on both synthetic data created with RAYSUM and real data of the Cascadia subduction zone with the conclusion that dipping discontinuities of up to 20° can be smoothly imaged. Furthermore, the subducting slab was shown to have a 4° southwards dip orthogonal to the convergence of the Juan de Fuca and the North American plate. Following the tests, the method is applied to the East African continent to create two almost continuous cross sections from the Afar Region to Cape Town. The cross sections are used to survey both the topography of the Mohorovičić (Moho) discontinuity and the mantle transition zone (MTZ) discontinuities at ∼410 and ∼660 km. Our images show that (1) the Moho is predominantly affected by Africa’s tectonic history, showing jumps at nearly every tectonic boundary with shallowing from northern Kenya towards the Afar region, and that (2) the MVZ is generally thinning from South Africa to the Afar region with an abrupt thickening towards the Arabian Peninsula. Both the shallowing of the Moho and the thinning of the MTZ are attributed to the mantle upwelling previously imaged by seismic tomography. The abrupt thickening of the MTZ in the north-east of the Afar region is attributed to a change in mantle flow direction which manifests in a steep, negative temperature gradient towards the Arabian peninsula in consistency with geodynamically modelled mantle flow

High-Resolution Ps Receiver Function Imaging of the Crust and Mantle Lithosphere Beneath Southern New England and Tectonic Implications

Southern New England exhibits diverse geologic features resulting from past tectonic events. These include Proterozoic and early Paleozoic Laurentian units in the west, several Gondwana-derived terranes that accreted during the Paleozoic in the east, and the Mesozoic Hartford Basin in the central part of the region. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) project involved the deployment of a dense array of 15 broadband seismometers across northern Connecticut to investigate the architecture of lithospheric structures beneath this region and interpret how they were created and modified by past tectonic events in the context of surface geology. We carried out P-to-S receiver function analysis on SEISConn data, including both single-station analysis and common conversion point (CCP) stacking. Our images show that the westernmost part of Connecticut has a much deeper Moho than central and eastern Connecticut. The lateral transition is a well-defined, ∼15 km step-like offset of the Moho over a ∼20 km horizontal distance. The Moho step appears near the surface boundary between the Laurentian margin and the Gondwana-derived Moretown terrane. Possible models for its formation include Ordovician underthrusting of Laurentia and/or modification by younger tectonic events. Other prominent features include a strong positive velocity gradient (PVG) beneath the Hartford basin corresponding to the bottom of the sedimentary units, several west-dipping PVGs in the crust and mantle lithosphere that may correspond to relict slabs or shear zones from past subduction episodes, and a negative velocity gradient (NVG) that may correspond to the base of the lithosphere

SPECFEM/specfem3d_globe: SPECFEM3D_GLOBE v8.1.0

<p>New in SPECFEM3D_GLOBE v8.1.0:</p> <ul> <li>adds EMC model support</li> <li>minor fixes and code improvements (including newer HIP and CUDA configuration)</li> <li>updates ADIOS2 and LIBXSMM calls</li> </ul> <p><em>with many thanks for contributions to this version</em>: Daniel Peter, Julien Thurin, Lucas Sawade</p&gt