Faculty Profiles - ITO Takeo

Papers - ITO Takeo

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Spatio-temporal afterslip distribution following the 2011 Tohoku-Oki earthquake using 3D viscoelastic Green's functions Reviewed

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

AIP Conference Proceedings Vol. 1987 ( 1987 ) page： 020056 2018.7

Preface: International Symposium on Earth Hazard and Disaster Mitigation 2017

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

AIP Conference Proceedings Vol. 1987 2018.7

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

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 Vol. 108 ( 4 ) page： 1918 - 1928 2018.6

Transient rheology of the oceanic asthenosphere following the 2012 Indian Ocean Earthquake inferred from geodetic data Reviewed

Cecep Pratama, Takeo Ito, Ryohei Sasajima, Takao Tabei, Fumiaki Kimata, Endra Gunawan, Yusaku Ohta, Tadashi Yamashina, Nazli Ismail, Irwandi Nurdin, Didik Sugiyanto, Umar Muksin, Irwan Meilano

JOURNAL OF ASIAN EARTH SCIENCES Vol. 147 page： 50 - 59 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

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 post seismic 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 x 10(17) Pas and 2 x 10(18) 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 Reviewed

Ryohei Sasajima, Takeo Ito

TECTONICS Vol. 36 ( 10 ) page： 1988 - 2021 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

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.
Plain Language Summary 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 the oceanic lithosphere using an analysis of the intraplate stress release due to oceanic intraplate earthquakes and found a significant anisotropy in the stress release in young oceanic lithosphere, that is, extensional stress release dominates in the ridge-parallel component while compressional stress release dominates in the spreading direction. Using a numerical simulation with the comparison to this observed result, we revealed that young oceanic lithosphere barely contracts in the ridge-parallel direction (only 0-25% of the spreading directional contraction rate), while it contracts freely in the spreading direction. The nearly free spreading directional contraction requires the smallness of the basal resistance traction on the bottom of the oceanic lithosphere, which implies the low-viscosity (weakness) of the oceanic asthenosphere. The ridge-parallel extensional thermal stress due to the estimated small ridge-parallel contraction may play a role in the weakening of the strength of the long oceanic transform faults; therefore, it may contribute to reduce the resistance to the seafloor spreading.

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 Reviewed

Cecep Pratama, Takeo Ito, Irwan Meilano, Andri Dian Nugraha

PROCEEDING OF THE 6TH INTERNATIONAL SYMPOSIUM ON EARTH HAZARD AND DISASTER MITIGATION (ISEDM) 2016 Vol. 1857 2017.7

Language：English Publishing type：Research paper (international conference proceedings) Publisher：AMER INST PHYSICS

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 0.4 + 0.13 g with COV 27% and 0.3 + 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 Reviewed

Takao Tabei, Fumiaki Kimata, Takeo Ito, Endra Gunawan, Hiroyuki Tsutsumi, Yusaku Ohta, Tadashi Yamashina, Yoshio Soeda, Nazli Ismail, Irwandi Nurdin, Didik Sugiyanto, Irwan Meilano

International Association of Geodesy Symposia Vol. 145 page： 21 - 28 2017

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Springer Verlag

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 Reviewed

Cecep Pratama, Takeo Ito, Takao Tabei

PROCEEDING OF THE 6TH INTERNATIONAL SYMPOSIUM ON EARTH HAZARD AND DISASTER MITIGATION (ISEDM) 2016 Vol. 1857 2017

Language：English Publishing type：Research paper (international conference proceedings) Publisher：AMER INST PHYSICS

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 x 10(22) N m and 0.2-0.3 x 10(22) 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 Reviewed

Agustan, Albertus Sulaiman, Takeo Ito

2nd International Conference of Indonesian Society for Remote Sensing (ICOIRS) Vol. 47 ( 1 ) 2016.12

Strain rate dependency of oceanic intraplate earthquake b-values at extremely low strain rates Reviewed

R.Sasajima and T. Ito

J. Geophys. Res 2016.6

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

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

Earth, Planets and Space 2016.4

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

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

J. Geophys. Res. Solid Earth Vol. 121 2016.3

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 ) page： 19-23 2016.3

Studies of Internal Structure of the Earth and Geodynamics based on Geodesy Invited Reviewed

Vol. 61 ( 1 ) page： 1-15 2015.4

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 Vol. 425 ( 37 ) page： 37-43 2015.2

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

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 page： Journal Asian Earth Sciences 2014

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

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

Journal of Geophysical Research 2012.5

Slip distribution of the 2011 off the Pacific coast of Tohoku Earthquake inferred from geodetic data Reviewed

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

Earth Planets Space Vol. 63 page： 627-630 2011.9

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 page： 112-121 2010.7

Spatio-temporal distribution of magma intrusions inducing repeated earthquake swarms off the east coast of the Izu peninsula, central Japan, for 1973-1998 Reviewed

Masayuki Murase, Takeo Ito, Yoshinari Hayashi, Takeshi Sagiya, Fumiaki Kimata and Hidefumi Watanabe

Journal of Volcanology and Geothermal Research Vol. 193 ( 1-2 ) page： 25-36 2010.3

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