Papers by Youichiro Takada
The role of rheological heterogeneities in postseismic deformation
<p>Advances in modelling and access to InSAR and GNSS observations have hig... more <p>Advances in modelling and access to InSAR and GNSS observations have highlighted the role that rheological heterogeneities play in postseismic deformation. Here we discuss three recent studies (Muto et al. 2019, Sambuddha et al. 2022, and Takada et al. in prep) following the 2011 Tohoku-Oki and 2008 Iwate-Miyagi earthquakes, which reveal both localised and along-strike rheological heterogeneities. We construct a self-consistent physical model of the postseismic deformation for these two events using the Unicycle code (Moore et al. 2019, Barbot, Moore, and Lambert 2017), with which we consider coupled fault slip and viscoelastic flow utilising laboratory-derived constitutive laws to simulate the time series of geodetic observations. All three studies illuminate a crustal low viscosity rheological heterogeneity in the vicinity of Mt Kurikoma / Mt Naruko. This is perhaps to be expected, given the proximity to known active volcanic centres, and is commensurate with observations following the 2016 Kumamoto earthquake (Moore et al. 2017) where we found low-viscosity anomalies beneath Mt Aso and Mt Kuju. However, the heterogeneities the data reveal are not restricted to known volcanic regions, because our results also suggest along-arc heterogeneity in the forearc mantle rheology of north-eastern Japan; specifically we find a narrower cold nose in the Miyagi region and wider for the Fukushima forearc. We also find evidence of interaction between the localized crustal heterogeneity and afterslip in both events, highlighting the importance of addressing mechanical coupling for long-term studies of postseismic relaxation. Variations in rheological properties in the lithosphere are not restricted to viscous and thermal effects, and observations of the Iwate-Miyagi earthquake suggest elastic heterogeneities may also play a role. We therefore conclude by presenting expressions for computing displacements and stress due to localised (faulting) and distributed inelastic deformation in heterogeneous elastic spaces with piece-wise constant homogeneous elastic subregions (Sato & Moore 2022), and their application in the context of the seismic cycle.</p><p> </p><p>Muto J, Moore J D P, Barbot S, Iinuma T, Ohta Y, Horiuchi S, Hikaru I, 2019. <em>Coupled afterslip and transient mantle flow after the 2011 Tohoku earthquake</em>. Science Advances</p><p>Dhar S, Muto J, Ito Y, Muira S, Moore J D P, Ohta Y, Iinuma T, 2022. <em>Along-Arc Heterogeneous Rheology Inferred from Postseismic deformation of the 2011 Tohoku-oki Earthquake</em>.</p><p>Moore J D P, Barbot S, Feng L, Hang Y, Lambert V, Lindsey E, Masuti S, Matsuzawa T, Muto J, Nanjundiah P, Salman R, Sathiakumar S, & Sethi H, 2019. jdpmoore/unicycle: Unicycle. <em>In Coupled afterslip and transient mantle flow after the 2011 Tohoku earthquake, Science Advances 2019</em>. Zenodo. https://doi.org/10.5281/zenodo.5688288</p><p>Barbot S, Moore J D P, Lambert V, 2017. <em>Displacements and stress associated with distributed anelastic deformation in a half-space.</em> BSSA</p><p>Moore J D P, Yu H, Tang C, Wang T, Barbot S, Peng D, Masuti S, Dauwels J, Hsu Y, Lambert V, Nanjundiah P, Wei S, Lindsey E, Feng L, Shibazaki B, 2017. <em>Imaging the distribution of transient viscosity after the 2016 Mw7.1 Kumamoto earthquake.</em> Science</p><p>Sato D, Moore J D P, 2022. <em>Displacements and stress associated with localised and distributed inelastic deformation with piecewise-constant elastic variations.</em></p>
Characteristics of the northernmost part of the surface rupture associated with the 2008 Iwate-Miyagi Nairiku, Japan, earthquake
Observation of aseismic crustal deformation in Taiwan by analysis of InSAR and GPS data
Japan Geoscience Union, 2017
Japan Geoscience Union, 2015
I introduce recent two extensive surveys conducted in and around the Atotsugawa fault system. Fir... more I introduce recent two extensive surveys conducted in and around the Atotsugawa fault system. First is the joint seismic observation by university group during 2004 to 2008. With this seismic data, I have estimated the focal mechanisms of small earthquakes and tectonic stress field by using stress inversion methods. Second is to estimate the inter-seismic crustal deformation with very high spatial resolution using GNSS and InSAR time series analysis. The estimated stress rotation can be explained by a viscoelastic dislocation model assuming cumulative slip deficit relative to surrounding part up to several tens of meters. On the other hand, the geodetic data indicate strain concentration near the fault trace, which may require a minor change of the fault model. However, the velocity fields still include systematic error coming from atmospheric and/or tropospheric disturbances. Farther noise reduction is required to constrain the physical model.
Japan Geoscience Union, 2014
Various types of seismic studies, including EEW systems, require automated programs for the accur... more Various types of seismic studies, including EEW systems, require automated programs for the accurate picking of P and S wave arrival times. The study on automatic picking was started in the late 1970 decade; however, even now, the accuracy is low and not suitable for detailed studies. We developed a new method of automatic picking, which is similar with the software used in computer chess games. The method defines an initial model of evaluation equation, which can select actual P and S wave arrival times among candidates by using values that show the characteristics of waveforms in time periods between candidates and about 100 unknown coefficients. By using a large number of waveform data together with manually picked P and S wave data, the unknown coefficients are determined such that the square of arrival time differences between manually picking and by the evaluation equation is minimized. It takes only 0.1 sec in the calculation of the evaluation equation for 10,000 events; very...
The Taiwan orogeny is result of the continental collision between the Luzon arc on the Philippine... more The Taiwan orogeny is result of the continental collision between the Luzon arc on the Philippine Sea plate and the Eurasian continental margin. GNSS velocity field indicates rapid and on-going east-west compression (e.g., Yu et al., 1997; Tsai et al., 2015). Due to such background compression, very rapid uplift up to 37 mm/yr has been aseismically proceeding in the southwestern part of Taiwan, which is detected by levelling and InSAR measurements (Ching et al., 2016; Tsukahara and Takada, 2018). Tsukahara and Takada (2018) showed that such rapid uplift cannot be explained solely by fault motion, and they concluded that a fold growth would contribute to the uplift motion as suggested by Ching et al. (2016). Actually, mud diapirs are widely distributed from South China Sea to the coastal area of Southwest Taiwan, and some of those are observed as mud volcanoes on land (e.g., Lin et al., 2009; Hsu et al., 2013; Doo et al., 2015). From physical point of view, mud diapirism can be regar...
Earth, Planets and Space, 2020
We applied differential InSAR analysis to the Shiretoko Peninsula, northeastern Hokkaido, Japan. ... more We applied differential InSAR analysis to the Shiretoko Peninsula, northeastern Hokkaido, Japan. All the interferograms of long temporal baseline (~ 3 years) processed from SAR data of three L-band satellites (JERS-1, ALOS, ALOS-2) commonly indicate remarkable phase changes due to the landslide movement at the southeastern flank of Mt. Onnebetsu-dake, a Quaternary stratovolcano. The area of interferometric phase change matches to known landslide morphologies. Judging from the timing of the SAR image acquisitions, this landslide has been moving at least from 1993 to the present. Successive interferograms of 1-year temporal baseline indicate the temporal fluctuation of the landslide velocity. Especially for the descending interferograms, the positive line-of-sight (LOS) length change, which indicates large subsidence relative to the horizontal movement, is observed in the upslope section of the landslide during 1993–1998, while the negative LOS change is observed in the middle and the...
Journal of Geography (Chigaku Zasshi), Oct 25, 2019
Report of the 2015 IUGG general assembly
journal of the geodetic society of japan, 2015
Recent crustal deformation and comparison among geodetic, seismological, and geological strain rate in the San-in shear zone
Japan Geoscience Union, 2016
Japan Geoscience Union, 2018
Synthetic aperture radar Interferometry (InSAR) is a versatile tool for the crustal deformation m... more Synthetic aperture radar Interferometry (InSAR) is a versatile tool for the crustal deformation monitoring with all-weather capability without any ground-based instrumentation in the target area. For a heavily vegetated region L-band SAR is advantageous to get good coherence. As a matter of fact, the L band SAR sensors installed in JERS, ALOS, and ALOS2, which are series of Japanese satellites operating on L band, have been providing many important results for both scientific and disaster mitigation purposes. Space-borne InSAR is thus already a standard method for volcanic crustal deformation monitoring. On the other hand, airborne InSAR still remains in a premature stage because of the difficulty of achieving effective method to mitigate problems caused by imperfect repeatability of the aircraft flight trajectory. To demonstrate the capability of L-band airborne SAR interferometery for volcanic crustal deformation monitoring, we are in the process of developing a standardized proce...
Earth, Planets and Space, 2017
A right-lateral shear zone in the San-in region, southwest Japan, has been proposed by previous g... more A right-lateral shear zone in the San-in region, southwest Japan, has been proposed by previous geological and seismological studies. It locates 350 km north of the Nankai Trough, that is, the main plate boundary between the subducting Philippine Sea and overriding Amurian plates and presumably accommodates a part of the relative plate motion. We present a geodetic evidence of the proposed shear zone using GNSS velocity data. Distinct shear deformation is identified only between ~132.5°E and ~135°E along a coastline which is a part of the proposed shear zone, and we propose to call the geodetically identified shear zone as the San-in shear zone (SSZ). The SSZ is a concentrated deformation zone with a width of ~50 km and can be modeled by a deep creep on a vertical strike slip fault with a creep rate of ~5 mm/year. There are some active faults parallel and oblique to the overall trend of the SSZ, but no single active fault coincides with the SSZ. Lineaments of microseismicity and source faults of large earthquakes are almost oriented in NNW-SSE in the SSZ and oblique to the overall trend of the SSZ. They are interpreted as conjugate Riedel shears. Based on these geodetic, seismological, and geomorphological observations, we suggest that the SSZ is a developing and young shear zone in a geological time scale.
Natural Disaster Science and Mitigation Engineering: DPRI reports, 2013
The Tohoku earthquake of March 11, 2011 caused a remarkably large deformation over Honshu, Japan.... more The Tohoku earthquake of March 11, 2011 caused a remarkably large deformation over Honshu, Japan. By analyzing ALOS/PALSAR data, up to 3.6 m of range increase at the tip of the Oshika peninsula, the closest point to the epicenter, was detected from ascending orbits. Combining ascending and descending interferograms, this peninsula was confirmed to have subsided and shifted eastward. This deformation may have caused by huge reverse slip on the plate interface near the trench axis. This large deformation induced activities of local earthquakes of magnitude 6 or larger, and volcanic unrests. Among them, the April 11 M7.0 event that occurred in southern Fukushima Prefecture occurred on previously unrecognized active faults. More than 9 fringes showing range increase were found in the vicinity of the epicenter of the Fukushima event. This observation is consistent with normal faulting on faults, whose motion was previously not recognized. We also found slight range increase in volcanic regions in Tohoku. These observations imply the March 11 shock induced large extensional stress in the crust of eastern Japan.
Bulletin of the Seismological Society of America, 2010
We use crustal deformation data sets derived from satellite-based synthetic aperture radar (SAR) ... more We use crustal deformation data sets derived from satellite-based synthetic aperture radar (SAR) to develop a fault source model of the 2008 M w 7.9 Wenchuan earthquake, China, that occurred at the Longmen Shan fault zone. The data sets include interferometric SAR (InSAR), range offset, and azimuth offset data acquired at seven ascending paths. The range and azimuth offset data are particularly important, exhibiting a single major rupture to the northeast (NE) and multiple ruptures to the southwest (SW). Our preferred model consists of six segments; four follow the previously mapped traces of the Beichuan fault (BF) and its NE extension, one corresponds to the Pengguan fault (PF) to the SW, and the other is included to represent a conjugate fault to the SW. Fixing the location and geometry of those segments, we solve the variable slip distribution whose patch size increases toward the greater depth; we use a nonnegative least-squares method with a smoothing constraint on the distributed slip. The geodetically estimated moment is 1:05 × 10 21 N m (M w 7:9), which is close to the seismological estimate and suggests that there are insignificant postseismic signals in the data. Maximum slip of ∼10 m, consisting of both thrust and right-lateral slip components, is identified at the shallowest patches to the NE along the BF. The multiple fault segments to the SW show that the thrust slip component initially dominates, and the strike slip becomes significant toward the NE. Examining the sensitivity of the predicted azimuth offset data to the assumed dip angle, we found that the dip angle changed significantly from 35°-45°at the SW fault segment for the PF to 80°-90°at the NE extension of the BF.
Ground deformation associated with the 2008 Sichuan Earthquake in China, estimated using a SAR offset-tracking method
ABSTRACT Introduction: A catastrophic earthquake struck China"fs Sichuan area on May 12,... more ABSTRACT Introduction: A catastrophic earthquake struck China"fs Sichuan area on May 12, 2008, with the moment magnitude of 7.9 (USGS). The hypocenter and their aftershocks are distributed along the western edge of the Sichuan Basin, suggesting that this seismic event occurred at the Longmeng Shan fault zone which is constituted of major three active faults (Wenchuan-Maowen, Beichuan, and Pengguan faults). However, it is unclear whether these faults were directly involved in the mainshock rupture. An interferometry SAR (InSAR) analysis generally has a merit that we can detect ground deformation in a vast region with high precision, however, for the Sichuan event, the surface deformation near the fault zone has not been satisfactorily detected from the InSAR analyses due to a low coherency. An offset-tracking method is less precise but more robust for detecting large ground deformation than the interferometric approach. Our purpose is to detect the detail ground deformation immediately near the faults involved in the Sichuan event with applying the offset-tracking method. Analysis Method: We analyzed ALOS/PALSAR images, which have been taken from Path 471 to 476 of ascending track, acquired before and after the mainshock. We processed SAR data from the level-1.0 product, using a software package from Gamma Remote Sensing. For offset-tracking analysis we adopt intensity tracking method which is performed by cross-correlating samples of backscatter intensity of a master SAR image with samples from the corresponding search area of a slave image in order to estimate range and azimuth offset fields. We reduce stereoscopic effects that produce apparent offsets, using SRTM3 DEM data. Results: We have successfully obtained the surface deformation in range (radar look direction) component, while in azimuth (flight direction) no significant deformation can be detected in some orbits due to "gazimuth streaks"h that are errors caused by ionospheric effects. Some concluding remarks are as follows: On the Beichuan F. and its northeastward extension, a clear boundary of a motion toward and away from the satellite can be recognized just along the fault, which is almost consistent with a right-lateral fault motion. On the other hand, in the southwestern region from the Beichuan city where the three major faults are running almost parallel, two boundaries of motions can be recognized; On the Beichuan F. there are a clear displacement boundary in range component, while on the Pengguan F. a boundary can be identified in azimuth component rather than in range, suggesting that the seismic ruptures proceeded with different fault motions at each fault. For the Wenchuan-Maowen F., no significant displacement boundary can be recognized. Acknowledgments: PALSAR data are provided from Earthquake Working Group and PIXEL (PALSAR Interferometry Consortium to Study our Evolving Land surface) under a cooperative research contract with JAXA. The ownership of PALSAR data belongs to METI (Ministry of Economy, Trade and Industry) and JAXA.
Journal of Geography (Chigaku Zasshi), Oct 25, 2019
MOESM1 of Aseismic fold growth in southwestern Taiwan detected by InSAR and GNSS
Additional file 1. This file contains additional figures of interferograms, fault models, and rel... more Additional file 1. This file contains additional figures of interferograms, fault models, and related information.
Precursory ground deformation prior to the 2018 phreatic eruption of Kirishima Iwo-Yama volcano, Japan, revealed by airborne and spaceborne InSAR
Japan Geoscience Union, 2020
Japan Geoscience Union, 2019
Although Airborne SAR is advantageous in terms of flexibility of flight path direction and observ... more Although Airborne SAR is advantageous in terms of flexibility of flight path direction and observation scheduling, the deviation from the flight path linearity due to the perturbation by wind irregularity makes interferometry difficult. We have been working on a development of L band airplane SAR interferometric technique with an aim to use it for volcanic deformation monitoring. The most effective way to improve the coherence between 2 airborne observations is precise coregistration of the slave image against the master image. We here present a new method of precise coregistraion for airborne SAR interferometry using pixel by pixel resampling capability of RINC software package developed by Taku Ozawa at NIED. We demonstrate the usefulness of this technique utilizing airborne repeat path SAR data acquired by JAXA’s airborne L-band SAR system (pi-sar-l2) over southern Kyushu volcanoes (Sakurajima volcano, Kirishima volcano and Unzen volcano) .
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Papers by Youichiro Takada