المؤلفون: En Jui Lee, Po Chen, Thomas H. Jordan, L. Wang

مصطلحات موضوعية: Geology, Computational seismology, Early warning, Earthquake ground motions, Earthquake source observations, Probability distributions, Wave propagation

الوصف: A central problem of seismology is the inversion of regional waveform data for models of earthquake sources. In regions such as Southern California, preliminary 3-D earth structure models are already available, and efficient numerical methods have been developed for 3-D anelastic wave-propagation simulations. We describe an automated procedure that utilizes these capabilities to derive centroid moment tensors (CMTs). The procedure relies on the use of receiver-side Green's tensors (RGTs), which comprise the spatial-temporal displacements produced by the three orthogonal unit impulsive point forces acting at the receivers. We have constructed a RGT database for 219 broad-band stations in Southern California using a tomographically improved version of the 3-D SCEC Community Velocity Model Version 4.0 (CVM4) and a staggered-grid finite-difference code. Finite-difference synthetic seismograms for any earthquake in our modelling volume can be simply calculated by extracting a small, source-centred volume from the RGT database and applying the reciprocity principle. The partial derivatives needed for the CMT inversion can be generated in the same way. We have developed an automated algorithm that combines a grid-search for suitable focal mechanisms and hypocentre locations with a Gauss-Newton optimization that further refines the grid-search results. Using this algorithm, we have determined CMT solutions for 165 small to medium-sized earthquakes in Southern California. Preliminary comparison with the CMT solutions provided by the Southern California Seismic Network (SCSN) shows that our solutions generally provide better fit to the observed waveforms. When applied to a large number of earthquakes, our algorithm may provide a more robust CMT catalogue for earthquakes in Southern California.

العلاقة: https://figshare.com/articles/journal_contribution/Rapid_Full-Wave_Centroid_Moment_Tensor_CMT_Inversion_in_a_Three-Dimensional_Earth_Structure_Model_for_Earthquakes_in_Southern_California/13678024Test

الإتاحة: https://doi.org/10.1111/j.1365-246x.2011.05031.xTest
https://figshare.com/articles/journal_contribution/Rapid_Full-Wave_Centroid_Moment_Tensor_CMT_Inversion_in_a_Three-Dimensional_Earth_Structure_Model_for_Earthquakes_in_Southern_California/13678024Test

المؤلفون: Harm J. A. Van Avendonk, W. Steven Holbrook, Daniel Lizarralde, Mauricio M. Mora, Steven H. Harder, Andrew D. Bullock, Guillermo E. Alvarado, Carlos J. Ramírez

مصطلحات موضوعية: Geology, Body waves, Continental margins: convergent, Controlled source seismology, Subduction zone processes, Wave propagation

الوصف: In the 2005 TICOCAVA explosion seismology study in Costa Rica, we observed crustal turning waves with a dominant frequency of ~10 Hz on a linear array of short-period seismometers from the Pacific Ocean to the Caribbean Sea. On one of the shot records, from Shot 21 in the backarc of the Cordillera Central, we also observed two seismic phases with an unusually high dominant frequency (~20 Hz). These two phases were recorded in the forearc region of central Costa Rica and arrived ~7 s apart and 30-40 s after the detonation of Shot 21. We considered the possibility that these secondary arrivals were produced by a local earthquake that may have happened during the active-source seismic experiment. Such high-frequency phases following Shot 21 were not recorded after Shots 22, 23 and 24, all in the backarc of Costa Rica, which might suggest that they were produced by some other source. However, earthquake dislocation models cannot produce seismic waves of such high frequency with significant amplitude. In addition, we would have expected to see more arrivals from such an earthquake on other seismic stations in central Costa Rica. We therefore investigate whether the high-frequency arrivals may be the result of a deep seismic reflection from the subducting Cocos Plate. The timing of these phases is consistent with a shear wave from Shot 21 that was reflected as a compressional (S×P) and a shear (S×S) wave at the top of the subducting Cocos slab between 35 and 55 km depth. The shift in dominant frequency from ~10 Hz in the downgoing seismic wave to ~20 Hz in the reflected waves requires a particular seismic structure at the interface between the subducting slab and the forearc mantle to produce a substantial increase in reflection coefficients with frequency. The spectral amplitude characteristics of the S×P and S×S phases from Shot 21 are consistent with a very high Vp/Vs ratio of 6 in ~5 m thick, slab-parallel layers. This result suggests that a system of thin shear zones near the plate interface beneath the forearc ...

العلاقة: https://figshare.com/articles/journal_contribution/Seismic_Evidence_for_Fluids_in_Fault_Zones_on_Top_of_the_Subducting_Cocos_Plate_Beneath_Costa_Rica/13678009Test

الإتاحة: https://doi.org/10.1111/j.1365-246x.2010.04552.xTest
https://figshare.com/articles/journal_contribution/Seismic_Evidence_for_Fluids_in_Fault_Zones_on_Top_of_the_Subducting_Cocos_Plate_Beneath_Costa_Rica/13678009Test

المؤلفون: Özgün, Özlem, Apaydın, Gökhan, Kuzuoğlu, Mustafa, Sevgi, Levent

المساهمون: Doğuş Üniversitesi, Mühendislik Fakültesi, Elektronik ve Haberleşme Mühendisliği Bölümü, TR52403, TR11882, TR164994, TR143819, Sevgi, Levent

مصطلحات موضوعية: Path Loss Predictions, Wave-Propagation, Calibration, Tool

الوصف: The above paper [1] is about the two-way split-step parabolic equation method (2W-SSPE) over irregular terrain, and claims that they have developed the “improved” version of the 2W-SSPE approach that has been proposed and validated by us in literature [2]-[11]. The paper [1] claims to derive the 2W-PE directly from 2D Helmholtz equation. They do this by listing and explaining equations (1)-(9). The authors needed to state that this is quite different from the formulation given in Levy's book (reference [9] in [1]). Actually, factorization before or after does not mean anything; their equations (8) and (9) are exactly the same. As a result listing equations (1)-(9) does not mean derivation of the new two-way PE. ; IEEE Antennas and Propagation Society

وصف الملف: application/pdf

العلاقة: IEEE Transactions on Antennas and Propagation; Diğer; ÖZGÜN, Ö., APAYDIN, G., KUZUOĞLU, M., SEVGİ, L. (2014). Comments on "propagation modeling over irregular terrain by the improved two-way parabolic equation method". IEEE Transactions on Antennas and Propagation, 62 (7), pp. 3894-3894. https://dx.doi.org/10.1109/TAP.2014.2328018Test.; 000340098600055 (WOS); 14429540 (INSPEC); https://dx.doi.org/10.1109/TAP.2014.2328018Test; https://hdl.handle.net/11376/1812Test; 62; 3894

الإتاحة: https://doi.org/10.1109/TAP.2014.2328018Test
https://hdl.handle.net/11376/1812Test

المؤلفون: de Juli, MC, Falceta-Goncalves, D, Jatenco-Pereira, V

المساهمون: Jatenco-Pereira, V, Chian, ACL, ValdesGalicia, JF, Shea, MA

المصدر: de Juli , MC , Falceta-Goncalves , D & Jatenco-Pereira , V 2005 , Alfven waves propagation in homogeneous and dusty astrophysical plasmas . in V Jatenco-Pereira , ACL Chian , JF ValdesGalicia & MA Shea (eds) , Fundamentals of Space Environment Science . ADVANCES IN SPACE RESEARCH , vol. 35 , PERGAMON-ELSEVIER SCIENCE LTD , KIDLINGTON , pp. 925-935 , 1st Latin-American Advanced School on Space Environment , San Jose dos Campos , Brazil , 22/03/04 . https://doi.org/10.1016/j.asr.2005.03.143Test

مصطلحات موضوعية: Alfven waves, magnetized dusty plasmas, wave propagation, LOW-FREQUENCY WAVES, WOLF-RAYET STARS, STELLAR WINDS, MASS-LOSS, MOLECULAR CLOUDS, CIRCUMSTELLAR ENVELOPE, PHYSICAL CONDITIONS, RADIATION PRESSURE, SIZE DISTRIBUTION, MAGNETIC-FIELDS

الوصف: Astrophysical plasma coexist with dust particles in many situations. These particles are charged either negatively or positively depending on their surrounding plasma environments. This system of such charged dust, electrons, and ions forms a so-called dusty plasma. We discuss the effects of the dust particles on the propagation and absorption of the Alfven waves in (i) stellar winds and (ii) in star formation regions. In both cases, we have shown the importance of a strong damping of Alfven waves due to the dust and the consequences for wind acceleration and the changes in the Jeans length related to the star formation process. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

الإتاحة: https://doi.org/10.1016/j.asr.2005.03.143Test
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/alfven-wavesTest-propagation-in-homogeneous-and-dusty-astrophysical-plasmas(30471969-deac-440d-aa32-8682e9d59c2e).html