Article
Geochemistry & Geophysics
F. De Martin, E. Chaljub, P. Thierry, P. Sochala, F. Dupros, E. Maufroy, B. Hadri, A. Benaichouche, F. Hollender
Summary: The study conducted a global sensitivity analysis to determine the most influential physical parameters when predicting earthquake ground motions in a 3-D sedimentary basin. Findings revealed that the quality factor Qs significantly affected the peak ground motions (PGMs) in the middle of the basin, while the geological layering configuration had a strong influence on PGMs near the basin edges. Additionally, the shear wave velocity at the free surface and the bedrock underlying the basin were found to equally influence PGMs in different areas of the basin.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Marta Pienkowska, Vadim Monteiller, Tarje Nissen-Meyer
Summary: This paper presents a new method for studying wave propagation that can decipher small structures inside the Earth at high resolution. The method combines a global Green's functions database with a local 3-D model, offering flexibility and the ability to couple 3-D wavefields, suitable for wave propagation applications in various fields.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Yongxin Gao, Ting Li, Guanqun Zhou, Chieh-Hung Chen, Yang-Yi Sun, Xuemin Zhang, Jann-Yenq Liu, Jian Wen, Cheng Yao, Xiaodong Bai
Summary: An analytically based method is proposed to simulate the acoustic-gravity waves in the horizontally stratified atmosphere-Earth structure. It solves the linear momentum, continuity and adiabaticity equations in the atmosphere and elastodynamic equations in the solid Earth. Numerical simulations are conducted to investigate the properties of the acoustic-gravity waves.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Acoustics
Ying He, Xueling Chen, Zhongxian Liu, Dejian Yang, Hai Zhang
Summary: This study developed an effective simulation method for multiple-station spatially correlated earthquake ground motions. The results show that local site conditions and medium saturation significantly affect the ground motions, especially in the long-period range. It is important to consider spatially varying ground motions with rational consideration of local site effects and medium saturation in seismic analysis of large-span structures.
SHOCK AND VIBRATION
(2021)
Article
Geochemistry & Geophysics
Chloe Gradon, Philippe Roux, Ludovic Moreau, Albanne Lecointre, Yehuda Ben Zion
Summary: The study analyzed the localizations near the San Jacinto fault in California using array processing techniques, finding that most localizations outside the fault could be attributed to surface structures excited by wind, while some under the fault may be caused by earthquakes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
S. Adourian, C. Lyu, Y. Masson, F. Munch, B. Romanowicz
Summary: In this study, we propose a general framework called 'box tomography' that couples different numerical seismic wave propagation solvers. This approach aims to reduce the computational cost of full-waveform inversion for structures within a target region when sources and receivers are located far from the region. We extend the implementation of this approach to a 3-D global elastic earth model, where both sources and stations are outside the target region. We demonstrate the efficiency and versatility of this approach through benchmark tests and believe it has great potential for imaging remote target regions in the deep mantle.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Chenglong Duan, David Lumley, Hejun Zhu
Summary: A new wave-equation imaging method has been developed to locate micro-earthquakes with increased resolution and reduced location errors. By separating and extrapolating P and S wavefields, as well as using three source imaging conditions, clean images without noisy artefacts have been obtained for microseismic source estimations. The method shows high resolution source location images and is relatively insensitive to ambient noise, providing accurate results for surface monitoring data.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Yujiang Xie, Catherine A. Rychert, Nicholas Harmon
Summary: The elastic and anelastic structures of the Earth provide fundamental constraints for understanding its physical and chemical properties. Deciphering small variations in seismic wave velocity and amplitude can be challenging, but advanced techniques such as full-waveform inversion can be useful.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Petros Bogiatzis, Catherine A. Rychert, Nicholas Harmon
Summary: The new shortest path method is efficient in accurately calculating travel times in large model spaces, outperforming conventional methods in terms of computational time and memory usage.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Engineering, Civil
Sun Yingchao, Yang Zailin, Yang Yong, Wang Guangyi
Summary: This study uses a theoretical approach to investigate the scattering problem of circular holes under a scalene triangle on the surface. By solving the Helmholtz equation that meets the zero-stress boundary conditions, the wave displacement function is obtained. Algebraic equations are established based on the complex function, multi-polar coordinate method, and region-matching technique. Numerical results show that the continuity of the auxiliary boundaries and the accuracy of the zero-stress boundaries are adequate, and the displacement of the free surface and the stress of the circular hole are related to various factors. Time-domain responses are calculated to reveal the wave propagation mechanism in a complicated structure.
EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION
(2022)
Article
Geochemistry & Geophysics
Ning Zhang, Jiasuo Pan, Yufeng Gao, Xin Chen, Denghui Dai, Yu Zhang
Summary: This study presents a method for analyzing the seismic response of semi-circular viscoelastic alluvial valleys under obliquely incident plane SH waves. Through numerical examples, it is found that the ground motion is sensitive to various factors, and the characteristics of ground motion of the central valley are further revealed.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Jing Ci Neo, Wenyuan Fan, Yihe Huang, David Dowling
Summary: The novel frequency-difference backprojection (FDBP) technique is developed and applied to imaging large earthquakes, showing promise in resolving complex earthquake rupture processes in tectonically complex regions.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Kees Wapenaar, Marcin Dukalski, Christian Reinicke, Roel Snieder
Summary: Many seismic imaging methods use wavefield extrapolation operators to redatum sources and receivers from the surface into the subsurface. We discuss wavefield extrapolation operators that account for internal multiple reflections, including propagator matrices, transfer matrices, and Marchenko focusing functions. These operators allow for accurate wavefield propagation and focusing in heterogeneous media, avoiding common approximations used in previous methods. Understanding the relationships between these operators can lead to new developments in Marchenko theory and improve applications in wavefield focusing, Green's function retrieval and imaging.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yann Capdeville
Summary: This work introduces a new method to replace Dirac point sources in seismic wave equations with a smooth source term using the non-periodic two-scale homogenization method, leading to accurate results in both far-source and near-source wavefields. The method has potential significance in solving forward and inverse seismic problems.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Christoph Sens-Schoenfelder, Ebru Bozdag, Roel Snieder
Summary: The rotation of the Earth affects the propagation of seismic waves, as the Coriolis force leads to global coupling between spheroidal and toroidal wave modes. Through wavefield simulations, it is shown that the Coriolis force can cause coupling and conversion between surface wave types depending on various factors. Resonant coupling gradually converts energy between different wave types, with location-dependent efficiency driven by equal phase velocities at specific periods.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geosciences, Multidisciplinary
Satoru Baba, Shunsuke Takemura, Kazushige Obara, Akemi Noda
GEOPHYSICAL RESEARCH LETTERS
(2020)
Article
Geochemistry & Geophysics
Takashi Furumura, Takuto Maeda
Summary: This paper introduces an efficient approach to high-resolution time-reversal source imaging simulation, which assimilates observational data to determine clearer source images, even for deep and distant earthquakes. This data-assimilated-based simulation method is effective for early forecasting of strong ground motions caused by large earthquakes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geosciences, Multidisciplinary
Shunsuke Takemura, Kazuo Yoshimoto, Katsuhiko Shiomi
Summary: The study conducted centroid moment tensor (CMT) inversions of moderate earthquakes in the Kanto region, Japan using a local 3D model, and investigated the effects on long-period ground motion simulations. Comparisons between 3D and 1D CMT solutions showed systematically smaller magnitudes in the 3D solutions. Differences in rigidity structures between 3D and 1D velocity models around the source regions explained the observed magnitude discrepancies.
EARTH PLANETS AND SPACE
(2021)
Article
Geochemistry & Geophysics
Takahiro Shiina, Takuto Maeda, Masayuki Kano, Aitaro Kato, Naoshi Hirata
Summary: An optimization method for applying the seismic-wave gradiometry method to a dense seismic station network with nonuniformly distributed seismographs was proposed, focusing on the Metropolitan Seismic Observation Network (MeSO-net) in Tokyo. Through numerical investigation, optimal shapes of weighting functions were found to greatly improve the reproducibility of seismic wavefields, especially when considering the direction of wave propagation.
SEISMOLOGICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Suguru Yabe, Satoru Baba, Takashi Tonegawa, Masaru Nakano, Shunsuke Takemura
Summary: This study analyzes shallow slow earthquakes along plate interfaces near trenches, observing heterogeneity in seismic energy radiation and longer recurrence intervals for tremors with higher energy rates. Seismic moment releases of shallow VLFEs are estimated using onshore seismic stations, with scaled energy ratios similar to those of deep slow earthquakes. Monitoring shallow VLFEs in the Japan Trench based on onshore data may miss a majority of seismic moment releases by small magnitude but frequent events.
Article
Geochemistry & Geophysics
K. Onodera, T. Kawamura, S. Tanaka, Y. Ishihara, T. Maeda
Summary: The study estimated scattering properties in the lunar crust through numerical simulations near the Apollo 12 landing site, successfully reproducing seismic signals excited by artificial impacts. It revealed the intense scattering structure extending down to 20 km in the northern region and to 10 km in the southern region from the landing site, requiring a smaller P- and S-wave velocity ratio compared to conventional values.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Article
Geosciences, Multidisciplinary
Yuta Amezawa, Takuto Maeda, Masahiro Kosuga
Summary: By investigating the relationship between the diffusivity of hypocenter migration and the duration of triggered earthquake swarms, a clear negative correlation was found. This suggests that diffusivity, crustal permeability, and fluid viscosity play a key role in controlling the duration of fluid-driven earthquake swarms.
EARTH PLANETS AND SPACE
(2021)
Article
Geochemistry & Geophysics
Satoru Baba, Kazushige Obara, Shunsuke Takemura, Akiko Takeo, Geoffrey A. Abers
Summary: The study revealed the presence of very low frequency earthquakes (VLFEs) around the Nicoya Peninsula, mainly near the trench axis and overlapping with large slip areas of slow slip events. Additionally, low frequency tremor signals were found to occur within the same time windows as VLFEs on high-frequency seismogram envelopes.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Geochemistry & Geophysics
Shunsuke Takemura, Kazushige Obara, Katsuhiko Shiomi, Satoru Baba
Summary: Cross-correlation analysis of long-term onshore broadband records revealed the distribution patterns of shallow very low frequency earthquakes (VLFEs) in the southeast region of the Kii Peninsula, Japan. The results showed that shallow VLFEs were widespread beneath the accretionary prism toe, but ones with large cumulative moments were localized around the western edge of the subducted paleo-Zenisu Ridge. The study suggested that the presence of the subducted ridge contributed to the occurrence of shallow slow earthquakes.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geosciences, Multidisciplinary
Shunsuke Takemura, Satoru Baba, Suguru Yabe, Kentaro Emoto, Katsuhiko Shiomi, Takanori Matsuzawa
Summary: Shallow very low frequency earthquakes (VLFEs) were detected off the Cape Muroto and Kii Channel in the Nankai subduction zone, and their moment rate functions were estimated. The swarms of VLFEs were considered as candidates for shallow slow slip events, and they exhibited similar scaling relationships between cumulative moments and activity areas, but varied in the relationship between cumulative moments and durations, which could be explained by along-strike variations in faulting conditions.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Takashi Tonegawa, Shunsuke Takemura, Suguru Yabe, Kiyoshi Yomogida
Summary: Fluid migration plays a crucial role in slow and megathrust earthquakes in subduction zones. This study shows that transient changes in seismic heterogeneity occur before shallow slow earthquakes in the Nankai subduction zone, Japan. The changes in heterogeneity primarily occur in the margin of the source region, indicating dynamic fluid migration. The timing of these changes reflects the pore pressure level in the corresponding source region.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geosciences, Multidisciplinary
Shunsuke Takemura, Kentaro Emoto, Lina Yamaya
Summary: By analyzing seismic waveforms observed at ocean-bottom seismometers (OBSs) and inland broadband seismometers, we found that coda amplitudes at OBSs were significantly larger than those at inland rock-site stations. Numerical simulations showed that the large coda amplitudes at OBSs were mainly due to multiple scattered waves within a thick sedimentary layer. However, the thick sedimentary layer had limited effects on the maximum S-wave amplitudes at OBSs.
EARTH PLANETS AND SPACE
(2023)
Correction
Geosciences, Multidisciplinary
Lina Yamaya, Kimihiro Mochizuki, Takeshi Akuhara, Shunsuke Takemura, Masanao Shinohara, Tomoaki Yamada
EARTH PLANETS AND SPACE
(2022)
Article
Geosciences, Multidisciplinary
Lina Yamaya, Kimihiro Mochizuki, Takeshi Akuhara, Shunsuke Takemura, Masanao Shinohara, Tomoaki Yamada
Summary: In this study, we conducted CMT inversion for small-to-moderate aftershocks in the off Ibaraki region of the 2011 off the Pacific coast of Tohoku earthquake using high-frequency seismograms and a reliable seismic velocity model. The CMT solutions revealed different characteristics of the aftershock activities, including thrust earthquakes, intraslab strike-slip earthquakes, intraslab normal-fault earthquakes, various earthquake focal mechanisms above a subducting seamount, and normal-fault earthquakes shallower than the interplate earthquakes.
EARTH PLANETS AND SPACE
(2022)
Review
Geosciences, Multidisciplinary
Shunsuke Takemura, Yohei Hamada, Hanaya Okuda, Yutaro Okada, Kurama Okubo, Takeshi Akuhara, Akemi Noda, Takashi Tonegawa
Summary: Slow earthquakes occur at deep and shallow plate boundaries along the Nankai Trough. Deep slow earthquakes are continuously distributed along the subducted Philippine Sea Plate, while shallow slow earthquakes occur in limited regions. Shallow slow earthquakes tend to be distributed in transitional regions between the frictionally locked and stably sliding zones on the plate boundary.
EARTH PLANETS AND SPACE
(2023)