Canadian Rockies and Alberta Network (CRANE)Since 2005, our group has been able to establish the first broadband seismic network in Alberta. The number of stations improved from the original 6 stations to more than 20 stations (and growing) in 2012. A large number of global earthquakes and small regional events have been recorded by CRANE. The data are continously being archived at the UofA and Alberta Geological Survey (AGS), our partner institution in regional seismic studies. Several studies have been published, or are in the process of being published (see below) in peer-revied geophysical journals. Included below are some pictures of the deployment and a recent overview,Overview Paper Gu, Y. J., A. Okeler, L. Shen, S. Contenti, The Canadian Rockies and Alberta Network (CRANE): New constraints on the Rockies and Western Canada Sedimentary Basin, Seismo. Res. Lett., 82, 575-588, 2011. click here to access Edmonton Journal article about the array Nordegg Mountaineer Journal article about the array CRANE Station Map Seismic Station Setup Field Photos images Link to Joint Project at AGS Alberta Earthquake Catalogue Open File Report (Stern, Schultz, Shen, Gu, Eaton) |
3-D Earth StructureThe first major global tomographic study of the Earth was made by Professor Adam M. Dziewonski in the early 70's. The idea of this study was that the travel time anomalies observed for many ray paths, criss-crossing the Earth between various points near the Earth's surface and reaching different depths in its interior, could be resolved formally into a three-dimensional (3-D) model. This procedure is now called `seismic tomography', as it conceptually resembles the medical CAT-SCAN procedures. The motivation for studying 3-D structure of the Earth's interior is that it may offer the best information on the dynamic processes in the deep interior of the Earth. As the seismic wave speeds change with temperature, it is plausible to obtain 3-D snapshots of the convection pattern in the Earth.Selected PublicationsShen, L., Y. J. Gu, Noise correlation tomography of the southern Western Canada Sedimentary Basin, J. Geophys. Res. , submitted, 2012.Liu, Q., Y. J. Gu, Seismic imaging: from classical to adjoint tomography, Tectonophysics , doi:10.1016/j.tecto.2012.07.006, 2012. [PDF] Gu, Y. J., A. Lerner-Lam, A. M. Dziewonski & G. Ekstrom, Seismic evidence for deep anisotropy beneath the East Pacific Rise, Earth Planet. Sci. Lett. , 232, 3-4, 259-272, 2005. [PDF] Gu, Y. J., A. M. Dziewonski, & Ekstrom, Simultaneous inversion for mantle shear velocity and topography of transition zone discontinuities, Geophys. J. Int., , 154 , 559-583, 2003. [PDF] Antolik, Gu, Dziewonski & Ekstrom, A new joint model of compressional and shear velocity in the mantle, Geophys. J. Int., , 153 , 443-466, 2003. [PDF] Gu, Y. J., A. M. Dziewonski, G. Ekstrom & W.-J. Su, Models of the mantle shear velocity and discontinuities in the pattern of lateral heterogeneities, J. Geophys. Res. , 106, 11169-11199, 2001. [PDF] |
Mantle Seismic DiscontinuitiesSharp changes in elastic properties and mineralogy are generally well known across the air-crust, crust-mantle, mantle-core, and outcore-innercore. What is less familiar to people outside the geophysical community is the presence of other known, or postulated seismic discontinuities at crust and mantle depths. These discontinuities (sometimes simply reflectors) embodies reatively abrupt changes in impedance (velocity * density) and could be detected by deep probing seismic waves. Among the most effective methods, small reflections and conversions, which often require phase enhancement to be detected reliably, can provide vital information on the depth, impedance contrast, dynamics and mineralogy surrounding mantle seismic discontinuities.Selected PublicationsGu, Y. J., A. Okeler, R. Schultz, Tracking slabs in the Western Pacific Subduction Zones, Earth Planet. Sci. Lett. , 331-332, 269-280, 2012. [PDF]Contenti, S., Y. J. Gu, A. Okeler, M. Sacchi, Shear wave reflectivity imaging of Nasca-South America subduction zone: stagnant slab in the mantle transition zone? Geophys. Res. Lett., 39 , L02310, doi:10.1029/2011GL050064, 2012. [PDF] . Gu, Y. J., Y. An, M. Sacchi, R. Schultz, J. Ritsema, Mantle reflectivity structure beneath oceanic hotspots, Geophys. J. Int. , doi:10.1111/j.1365-245X.2009.04042.x, 2009. [PDF] Gu, Y. J., A. M. Dziewonski, Global variability of transition zone thickness, J. Geophys. Res. , 107 , 2135, doi:10.1029/2001JB000489, 2002. [PDF] Gu, Y. J., A. M. Dziewonski, G. Ekstrom, Preferential detection of the Lehmann discontinuity beneath continents, Geophys. Res. Lett. , 28 , 4655-4658, 2001. [PDF] Gu, Y. J., A. M. Dziewonski, C. B. Agee, Global decorrelation of the topography of transition zone discontinuities, Earth Planet. Sci. Lett. , 157 , 57-67, 1998. [PDF] |
Microseismic SourcesAn area of growing public interest is microseismicity. The term microseismic suggests low amplitude, though the mechanisms and characteristics of many microseismic events are consistent with those with much greater magnitudes. Induced seismicity has gained signicant attention in recent years for the safty concerns industrial operations and fluid injections. Another type of microseism is ocean microseism caused by wave-coast impact or wave-wave interaction. My recent research has focused on both the regional microseicity/acquisition resolution and non-symmetric 'ambient' noise sources.PublicationsGu, Y. J., L. Shen, Gu, Y. J., L. Shen, Microseismic noise from large ice-covered lakes, Bull. Seis. Soc. Am. , 102, doi:10.1875/0120100010, 2012.Rodriguez, I. V., M. Sacchi, Y. J. Gu, Simultaneous recovery of origin time, hypocenter location, and seismic moment tensor using sparese representation theory, Geophys. J. Int. , 188, 1188-1202, 2012. Rodriguez, I. V., Y. J. Gu, and M. Sacchi, Resolution of seismic-moment tensor inversions from a single array of receivers, Bull. Seism. Soc. Am. , 101, 2634-2642, doi:10.1785/0120110016, 2011. Brzak, K., Y. J. Gu, A. Okeler, M. Steckler, and A. Lerner-Lam, Migratino imaging and forward modeling of microseismic noise sources near southern Italy, Geochem. Geophys. Geosys. , 10, Q01012, doi:10.1029/2008GC002234, 2009. [PDF] Gu. Y., C. Dublanko, A. Lerner-Lam, K. Brzak, M. steckler, Probing the sources of ambient seismic noise beneath Southern Italy, Geophys. Res. Lett., 34, L22315, doi:10.1029/2007GL031967, 2007. [PDF] |
Surface WavesSurface waves have contributed to our understanding of seismic velocities at crust and shallow mantle depths. A wide range of problems have involved processing and analysis of surface waves, whether it pertains to emissions from standard earthquake sources, or from environmental factors such as ocean wave impact or industrial traffic. Some of my past studies under the heading of "microseismic sources" are examples of the latter. Below is a list of papers that involves waveform fitting and inversion to improve regional seismic characterization of seismic structures.Selected PublicationsOkeler, A., Y. J. Gu, A. Lerner-Lam, M. Steckler, Seismic structure of the southern Apennines as revealed by waveform modelling of regional surface waves, Geophys. J. Int. , doi:10.1111/j.1365-246X.2009.04229.x, 2009. [PDF]Gu, Y. J, Probing the history of the Mathematician Paleoplate using surface waves Apennines as revealed by waveform modelling of regional surface waves, Tectonophysics, 424, 41-51, 2006. [PDF] Gu, Y. J, Probing the history of the Mathematician Paleoplate using surface waves, Tectonophysics, 424, 41-51, 2006. [PDF] Gu, Y. J, S. Web, A. Lerner-Lam, J. Gaherty, Upper mantle structure beneath the eastern Pacific Ocean ridges, J. Geophys. Res, 110, B063051, doi:10.1029/2004JB003381, 2005. [PDF] |
Seismic Method ImprovementsA significant part of my research is centered on improving seismic source and imaging techniques. The key is to bridge the gap between exploration seismics (known source, dense receivers) and the ever-improving broadband seismic analyses. Afterall, many of the same principles and methodologies are transferable when proper care and assumptions are taken. The collaboration between our group and the exploration seismic group headed by Dr. Mauricio Sacchi has ben particularly fruitful and will continue in the foreseeable future.Selected PublicationsRodriguez, I. V., M. Sacchi, Y. J. Gu, Simultaneous recovery of origin time, hypocenter location, and seismic moment tensor using sparese representation theory, Geophys. J. Int. , 188, 1188-1202, 2012.Gu, Y. J., Eds., Arrays and array methods in global seismology , 273 pages, Springer, Netherland, 2010. [Amazon] Le, L., Y. J. Gu, Y. Le., C. Chan, Probing long bones with ultrasonic body waves, Appl. Phys. Lett. , 96, 114102, 2010. Gu, Y. J., M. Sacchi, Radon transform methods in their applications in mapping mantle reflectivity structure, Surv. Geophys, doi:10.1007/s10712.009-9076-0, 2009. An, Y., Y. J. Gu, M. Sacchi, Imaging mantle discontinuities using least-squares Radon transform, J. Geophys. Res. , 112, doi:10.1029/2007JB005009, 2007. [PDF] Escalante, C., Y. J. Gu, M. Sacchi, Simultaneous iterative time-domain deconvolution to teleseismic receiver functions, Geophys. J. Int. , doi:10.1111.j.1365-246x.2007.03511.x , 2007. [PDF] Yang, X., Y. J. Gu, P. Shen, X. Liu, Z. Zheng, A study of the adaptive method for decoupling overlapped seismic records, Pure and Appl. Geophys. , 163 , 8, 1515-1536, 2006. [PDF] |