研究者詳細 - 伊藤　武男

論文 - 伊藤　武男

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Evaluation of the 2012 Indian Ocean coseismic fault model in 3-D heterogeneous structure based on vertical and horizontal GNSS observation, 査読有り

C. Pratama, T. Ito, T. Tabei, F. Kimata, E. Gunawan, Y. Ohta, T. Yamashina, I. Nurding, D. Sugiyanto, U. Muksin, N. Ismail, I. Meilano

AIP Conference Proceedings 1987 巻 ( 1987 ) 頁： 020011 2018年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AIP Conference Proceedings

Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include three-dimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrates best-fit calculation using scaling slip optimized to the horizontal or vertical observation lead the both fault model worsen the misfit of vertical or horizontal component, respectively. This result analysis indicates a trade-off between vertical and horizontal component and reflects the importance of revisiting the fault slip modeling incorporating vertical and horizontal data equally.

DOI： 10.1063/1.5047296

Web of Science

Scopus

Spatio-temporal afterslip distribution following the 2011 Tohoku-Oki earthquake using 3D viscoelastic green's functions 査読有り

Ito T., Suzuki S., Sato K., Hyodo M.

AIP Conference Proceedings 1987 巻 ( 1987 ) 頁： 020056 2018年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AIP Conference Proceedings

On March 11, 2011, the Tohoku-Oki earthquake (Mw 9.0) occurred on the plate interface of the subducting Pacific plate. During the co- and post-seismic periods, almost all GEONET and seafloor observations detected eastward crustal deformation. However, seafloor observations around main raptured zone moved in a westward direction during the post-seismic period. In this study, we estimate the spatio-temporal slip distribution during the co- and post-seismic periods from observed crustal deformations, such as GEONET and seafloor observations. For inversion, we use a viscoelastic Green's function derived from a three-dimensional finite element method considering the underground structure. The estimated maximum co-seismic slip is approximately 60m from the Japan Trench. Off Iwate prefecture, the moment magnitude and maximum afterslip 2.5 years after the Tohoku-Oki earthquake are approximately 8.13 and 2.0m, respectively. The afterslip distributions differ from the co-seismic slip distribution, and the relationship between the co-seismic and afterslip regions is complementary.

DOI： 10.1063/1.5047341

Web of Science

Scopus

Preface: International Symposium on Earth Hazard and Disaster Mitigation 2017

Meilano I., Cummins P., Zulfakriza , Ito T.

AIP Conference Proceedings 1987 巻 2018年7月

Coseismic Slip Distribution of the 2 July 2013 Mw 6.1 Aceh, Indonesia, Earthquake and Its Tectonic Implications 査読有り

Endra Gunawan, Sri Widiyantoro, Shindy Rosalia, Mudrik Rahmawan, Daryono, Irwan Meilano, Pepen Supendi, Takeo Ito, Takao Tabei, Fumiaki Kimata, Yusaku Ohta, Nazli Ismail

Bulletin of the Seismological Society of America 108 巻 ( 4 ) 頁： 1918 - 1928 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Bulletin of the Seismological Society of America

This study investigates the coseismic slip distribution of the 2 July 2013 Mw 6.1 Aceh earthquake using Global Positioning System (GPS) data, measured geological surface offsets, and an aftershock distribution for a period of four days after the mainshock. We use the aftershock distribution to constrain the fault-plane strike of a right-lateral fault identified as the Pantan Terong segment. We estimate the coseismic slip distribution with dip angle information from the Global Centroid Moment Tensor (CMT) (model 1) and U.S. Geological Survey (USGS) (model 2) catalogs. We also estimate the coseismic slip distribution using another two fault models. Model 3 is constructed on a left-lateral fault, the Celala segment, which is perpendicular to the Aceh segment of the Sumatran fault, and model 4 is constructed using the multiple faults in models 2 and 3. We further estimate the coseismic slip distribution of this earthquake by employing an elastic dislocation model, inverting only the GPS displacements for model 3 and jointly inverting GPS displacements and geological surface offsets for models 1, 2, and 4. Minimum misfit between data and model is obtained with model 3, suggesting that the earthquake slip occurred along a left-lateral fault. Analysis of stress transfer caused by the 2013 earthquake indicates that the stress level along the Pantan Terong segment is > 0:4 bar and the southeast part of Aceh segment was brought ∼0:3 bar closer to failure, suggesting a possible earthquake occurrence in the future. This work demonstrates that the seismicity-derived fault plane fails to predict the surface displacement, and that the inferred Celala segment produces positive stress on Pantan Terong segment and potentially triggered all the aftershocks.

DOI： 10.1785/0120180035

Web of Science

Scopus

Transient rheology of the oceanic asthenosphere following the 2012 Indian Ocean Earthquake inferred from geodetic data 査読有り

Pratama C., Ito T., Sasajima R., Tabei T., Kimata F., Gunawan E., Ohta Y., Yamashina T., Ismail N., Nurdin I., Sugiyanto D., Muksin U., Meilano I.

Journal of Asian Earth Sciences 147 巻頁： 50 - 59 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Asian Earth Sciences

Postseismic motion in the middle-field (100–500 km from the epicenter) geodetic data resulting from the 2012 Indian Ocean earthquake exhibited rapid change during the two months following the rupture. This pattern probably indicates multiple postseismic deformation mechanisms and might have been controlled by transient rheology. Therefore, the relative contribution of transient rheology in the oceanic asthenosphere and afterslip in the oceanic lithosphere should be incorporated to explain short- and long-term transitional features of postseismic signals. In this study, using two years of post-earthquake geodetic data from northern Sumatra, a three-dimensional spherical-earth finite-element model was constructed based on a heterogeneous structure and incorporating transient rheology. A rheology model combined with stress-driven afterslip was estimated. Our best-fit model suggests an oceanic lithosphere thickness of 75 km with oceanic asthenosphere viscosity values of 1 × 1017 Pa s and 2 × 1018 Pa s for the Kelvin and Maxwell viscosity models, respectively. The model results indicate that horizontal landward motion and vertical uplift in northern Sumatra require viscoelastic relaxation of the oceanic asthenosphere coupled with afterslip in the lithosphere. The present study demonstrates that transient rheology is essential for reproducing the rapidly changing motion of postseismic deformation in the middle-field area.

DOI： 10.1016/j.jseaes.2017.07.049

Web of Science

Scopus

Anisotropic Horizontal Thermal Contraction of Young Oceanic Lithosphere Inferred From Stress Release Due To Oceanic Intraplate Earthquakes 査読有り

Sasajima R., Ito T.

Tectonics 36 巻 ( 10 ) 頁： 1988 - 2021 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tectonics

How freely the oceanic lithosphere contracts horizontally due to thermal contraction is important information, because it reflects the boundary condition of the oceanic lithosphere, which includes information regarding the magnitude of driving/resisting forces of plate tectonics. We investigated the horizontal thermal contraction of young oceanic lithosphere using an analysis of the intraplate stress release due to oceanic intraplate earthquakes (OCEQs) and numerical simulations. The stress release due to OCEQs in young oceanic lithosphere (5–15 Ma) shows significant differences between the spreading directional component and the ridge-parallel component. The extensional stress release of the ridge-parallel component is 6 times as large as that of the spreading directional component, while the compressional stress release of the ridge-parallel component is one seventh that of the spreading directional component. We conducted a numerical simulation of the thermal stress evolution of the oceanic lithosphere to investigate how the difference in the horizontal contraction rates between the spreading direction and the ridge-parallel direction can explain the observed anisotropic stress release. The result indicates that young oceanic lithosphere (5–15 Ma) barely contracts in the ridge-parallel direction (only 0–30% of the spreading directional contraction rate), while it contracts freely in the spreading direction due to the weakness of the oceanic ridge strength and the low-viscosity asthenosphere. From the results, we constrained the magnitude of the basal traction working on the bottom of the oceanic lithosphere to be smaller than 0.44 MPa.

DOI： 10.1002/2017TC004680

Web of Science

Scopus

B-value and slip rate sensitivity analysis for PGA value in Lembang fault and cimandiri fault area 査読有り

Pratama C., Ito T., Meilano I., Nugraha A.

AIP Conference Proceedings 1857 巻 2017年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AIP Conference Proceedings

We examine slip rate and b-value contribution of Peak Ground Acceleration (PGA), in probabilistic seismic hazard maps (10% probability of exceedence in 50 years or 500 years return period). Hazard curve of PGA have been investigated for Sukabumi and Bandung using a PSHA (Probabilistic Seismic Hazard Analysis). We observe that the most influence in the hazard estimate is crustal fault. Monte Carlo approach has been developed to assess the sensitivity. Uncertainty and coefficient of variation from slip rate and b-value in Lembang and Cimandiri Fault area have been calculated. We observe that seismic hazard estimates are sensitive to fault slip rate and b-value with uncertainty result are 0.25 g dan 0.1-0.2 g, respectively. For specific site, we found seismic hazard estimate are 0.49 + 0.13 g with COV 27% and 0.39 + 0.05 g with COV 13% for Sukabumi and Bandung, respectively.

DOI： 10.1063/1.4987083

Web of Science

Scopus

Geodetic and geomorphic evaluations of earthquake generation potential of the northern Sumatran fault, Indonesia 査読有り

Tabei T., Kimata F., Ito T., Gunawan E., Tsutsumi H., Ohta Y., Yamashina T., Soeda Y., Ismail N., Nurdin I., Sugiyanto D., Meilano I.

International Association of Geodesy Symposia 145 巻頁： 21 - 28 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：International Association of Geodesy Symposia

We have conducted geodetic and geomorphic observations in the northernmost part of Sumatra, Indonesia to monitor strain accumulation in the vicinity of the northern Sumatran fault. Evaluation of the earthquake generation potential in this region is highly urgent because of a large fault slip rate, absence of major earthquakes for more than 100 years and recent Coulomb stress increase on the fault due to the 2004 Sumatra-Andaman earthquake (Mw 9:2).We have deployed Aceh GPS Network for the Sumatran Fault System (AGNeSS) since 2005. The data collected have been used for estimating slip/locking distribution of the Sumatran fault and constructing a comprehensive model for postseismic deformation after the 2004 event. Tectonic geomorphic features are also important to reveal long-term slip history of the fault. We have used high-resolution stereo-paired ALOS (Advanced Land Observing Satellite) PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping) satellite images to map the surface trace of the Sumatran fault and conducted field observations to ensure the trace by geomorphic and geologic evidence. We introduce preliminary results of the fault mapping together with a brief description of the crustal deformation field detected by GPS.

DOI： 10.1007/1345_2015_200

Scopus

Inhomogeneous spherical-earth finite element model of coseismic offset due to the 2012 Indian Ocean Earthquake 査読有り

Pratama C., Ito T., Tabei T.

AIP Conference Proceedings 1857 巻 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AIP Conference Proceedings

On April 11, 2012, a Mw 8.6 earthquake struck off the west coast of northern Sumatra approximately 300 km west of the Sunda trench following by Mw 8.2 two hours afterward. The 2012 Indian Ocean Earthquake sequence, which was the largest intraplate earthquake in recorded history, yielded seismic moment of 1.2-1.3 × 1022 N m and 0.2-0.3 × 1022 N m for the main shock (Mw 8.6) and the after shock (Mw 8.2), respectively. Aceh GPS Network for Sumatran Fault System (AGNeSS) observed a predominantly ENE coseismic offset up to 10 cm while the sites on the Andaman Island observed southward and southern part Sumatra GPS Array (SuGar) network observed northward. Limited far-field and inland GPS observation network might lead the homogeneous and half-space model insufficient to explain the coseismic offset. In that of sense, in order to estimate more realistic surface displacement due to complex subduction and far-field GPS station, we consider developing inhomogeneous three-dimensional finite element model incorporate subducting slab, three-dimensional velocity earth structure, realistic topography and bathymetry as well as sphericity of the earth. We calculate coseismic offset by forward modeling using slip distribution as reported from Wei et al. [7]. This study investigates the effect of inhomogeneous structure and spherical geometry model in reproducing actual coseimic offset due to 2012 Indian Ocean Earthquake.

DOI： 10.1063/1.4987066

Web of Science

Scopus

Measuring Deformation in Jakarta through Long Term Synthetic Aperture Radar (SAR) Data Analysis 査読有り

Agustan, Albertus Sulaiman, Takeo Ito

2nd International Conference of Indonesian Society for Remote Sensing (ICOIRS) 47 巻 ( 1 ) 2016年12月

Strain rate dependency of oceanic intraplate earthquake b-values at extremely low strain rates 査読有り

R.Sasajima and T. Ito

J. Geophys. Res 2016年6月

Co-seismic offsets due to two earthquakes (Mw 6.1) along the Sumatran fault system derived from GNSS measurements 査読有り

T. Ito, E. Gunawan, F. Kimata, T. Tabei, I. Meilano, Agustan, Y. Ohta, N. Ismail, I. Nurdin and D. Sugiyanto

Earth, Planets and Space 2016年4月

The Sensitivity of Surface Mass Loading Displacement Response to Peturbations in the Elastic Structure of the Crust and Mantle 査読有り

H. R. Martens, L. Rivera, M. Simons, and T. Ito

J. Geophys. Res. Solid Earth 121 巻 2016年3月

地震や火山の活動を捉えるミリメートル制度のGNSS観測

伊藤武男

名古屋大学理学部技術報告 ( 20 ) 頁： 19-23 2016年3月

測地学的手法を統合的に活用した地球内部構造とダイナミクスの解明招待有り査読有り

伊藤武男

測地学会誌 61 巻 ( 1 ) 頁： 1-15 2015年4月

海洋潮汐がトリガーとなる氷河地震

伊藤武男，古本宗充

月刊地球 425 巻 ( 37 ) 頁： 37-43 2015年2月

A comprehensive model of postseismic deformation of the 2004 Sumatra-Andaman earthquake deduced from GPS observations in northern Sumatra 査読有り

E. Gunawan, T. Sagiya, T. Ito, F. Kimata, T. Tabei, Y. Ohta, I. Meilano, H. Z. Abidine, Agustan, I. Nurdin and D. Sugiyanto

Journal Asian Earth Sciences 頁： Journal Asian Earth Sciences 2014年

Isolating along-strike variations in the depth extent of shallow creep and fault locking on the northern Great Sumatran Fault 査読有り

Ito, T., E. Gunawan, F. Kimata, T. Tabei, M. Simons, I. Meilano, Agustan, Y. Ohta, I. Nurdin, and D. Sugiyanto

Journal of Geophysical Research 2012年5月

Slip distribution of the 2011 off the Pacific coast of Tohoku Earthquake inferred from geodetic data 査読有り

Takeo Ito, Kazuhiro Ozawa, Tsuyoshi Watanabe, and Takeshi Sagiya

Earth Planets Space 63 巻頁： 627-630 2011年9月

Ground deformation detected by AGNeSS (Aceh GPS Network for Sumatran fault System) in North Sumatra after the 2004 Sumatra-Andaman earthquake

Endra Gunawan, Takeo Ito, Fumiaki Kimata, Takeshi Sagiya, Takao Tabei, Didik Sugiyanto/Irwandi, Irwan Meilano, Mipi A. Kusuma, Hasanuddin Z. Abidin, Agustan

The 6th Investigation Report of 2004 Northern Sumatra Earthquakes 頁： 112-121 2010年7月

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