Applying local Green's functions to study the influence of the crustal structure on hydrological loading displacements |
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| Affiliation: | 1. Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Section 1.3: Earth System Modelling, Germany;2. Charles University in Prague, Czech Republic;3. DIAS – Dublin Institute of Advanced Studies, Ireland;4. Utrecht University, The Netherlands;1. Department of Mechanical Engineering, École de Technologie Supérieure (ÉTS), Montréal, QC, Canada H3C 1K3;2. IRSST, Montréal, QC, Canada H3A 3C2;3. Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, QC, Canada J1K 2R1;1. Faculty of Geoscience and Environment Engineering, Southwest Jiaotong University, Chengdu 611756, China;2. State-province Joint Engineering Laboratory of Spatial Information Technology of High-speed Rail Safety, Chengdu 611756, China;3. School of Civil Engineering and Architecture, Southwest Petroleum University, Chengdu 610500, China;1. Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali, Università di Bologna, Italy;2. Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, Bologna, Italy;3. Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Italy;4. Dipartimento di Ingegneria Enzo Ferrari, Università degli Studi di Modena e Reggio Emilia, Modena, Italy;5. Dipartimento di Geofisica della Litosfera, Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste, Italy;6. Dipartimento di Storia Culture Civiltà, Università di Bologna, Italy;1. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China;2. Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan;1. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan;2. Department of Geosciences, National Taiwan University, Taipei, Taiwan;3. School of Earth, Environment and Society, Bowling Green State University, Bowling Green, OH, USA;4. Berkeley Seismological Laboratory, University of California, Berkeley, CA, USA;5. Department of Bioenvironmental System Engineering, National Taiwan University, Taipei, Taiwan;6. NTU Research Center for Future Earth, National Taiwan University, Taipei, Taiwan |
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| Abstract: | The influence of the elastic Earth properties on seasonal or shorter periodic surface deformations due to atmospheric surface pressure and terrestrial water storage variations is usually modeled by applying a local half-space model or an one dimensional spherical Earth model like PREM from which a unique set of elastic load Love numbers, or alternatively, elastic Green's functions are derived. The first model is valid only if load and observer almost coincide, the second model considers only the response of an average Earth structure. However, for surface loads with horizontal scales less than 2500 km2, as for instance, for strong localized hydrological signals associated with heavy precipitation events and river floods, the Earth elastic response becomes very sensitive to inhomogeneities in the Earth crustal structure.We derive a set of local Green's functions defined globally on a 1° × 1° grid for the 3-layer crustal structure TEA12. Local Green's functions show standard deviations of ±12% in the vertical and ±21% in the horizontal directions for distances in the range from 0.1° to 0.5°. By means of Green's function scatter plots, we analyze the dependence of the load response to various crustal rocks and layer thicknesses. The application of local Green's functions instead of a mean global Green's function introduces a variability of 0.5–1.0 mm into the hydrological loading displacements, both in vertical and in horizontal directions. Maximum changes due to the local crustal structures are from −25% to +26% in the vertical and −91% to +55% in the horizontal displacements. In addition, the horizontal displacement can change its direction significantly. The lateral deviations in surface deformation due to local crustal elastic properties are found to be much larger than the differences between various commonly used one-dimensional Earth models. |
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| Keywords: | Local Green's function Site-dependent load Love number Surface deformation Hydrological loading Scatter plot |
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