Features of seismic waves recorded by seismic exploration in 2002: Responses from valley structure of the bedrock beneath Mizuho Plateau

Seismic waves from natural sources were recorded in seismic exploration experiments in January 2002 by the 43rd Japanese Antarctic Research Expedition (JARE-43). Three kinds of seismic waves were recorded: (1) a teleseismic event occurred in the Kermadec Is. region, (2) local icequakes and (3) an unidentified event. The teleseismic waves show high signal-to-noise ratio in spite of the small magnitude of the event: this indicates that it is highly feasible to study not only the local shallow structure but also the deep structure of the earth by using teleseismic events. Frequency spectra of the waveforms show discordances along the observation line. The 2.0 Hz frequency component is very small in waveforms recorded by stations in the middle part of the observation line. On the other hand, the 1.5, 3.0 and 5.0 Hz frequency components are large in the records of these stations. These stations are located just above the valley topography of the interface between the ice sheet and the upper crust, which has been revealed by JARE-41 and JARE-43 seismological experiments

Vaginoplasty with a Pudendal-Thigh Flap in Intersexuals

We treated 2 different types of intersexual patients who underwent a vaginoplasty with the pudendal-thigh flap. One was a female with testicular feminization syndrome for whom we reconstructed the total vagina with a pudendal-thigh flap, and the other was a female with an adrenogenital syndrome for whom we enlarged the introitus of the vagina with the same approach. There were no complications such as a flap necrosis. In addition, there was no stricture of the neo-vagina and no urinary problem.</p

Gestational Outcomes and Birth Weight in Japanese Women at the Upper and Lower limits of the Normal BMI range

To examine the outcome of gestational blood pressure and birth weight in women with normal pre-pregnancy BMI (18.5-25 kg/m2) who are at the lower and upper limits of this range, i.e., slightly underweight or slightly overweight. Overall, 2,038 Japanese women with low -risk who had delivered during January 2014–December 2016 were classified according to their pre-pregnancy BMI: underweight (< 18.5 kg/m2), slightly underweight (18.5≤BMI<21 kg/m2), normal (21≤BMI<23 kg/m2), slightly overweight (23≤BMI<25 kg/m2) and overweight (≤ 25 kg/m2). Their blood pressure during each trimester and birth weight was evaluated. The slightly overweight group showed a significantly higher blood pressure than the underweight and slightly underweight groups. Birth weight was lower in the slightly underweight than in the slightly overweight group (p<0.01). The incidence rate of “heavy for dates” (HFD) infants was significantly higher in the slightly overweight and overweight groups than in the other groups (p<0.05 and p<0.01, respectively). Weight gain of < 7 kg significantly increased the rate of “light for dates” (LFD) infants, while a weight gain of ≥13 kg significantly increased the rate of HFD infants (p<0.05 and p<0.01, respectively). Blood pressure during pregnancy was ssociated with pre-pregnancy BMI. The birth weight of infants of low-risk pregnant women is affected by both pre-pregnancy BMI and gestational weight gain

Seismic refraction and wide-angle reflection exploration by JARE-43 on Mizuho Plateau, East Antarctica

The 43rd Japanese Antarctic Research Expedition (JARE-43) carried out seismic exploration experiments on Mizuho Plateau,East Antarctica,in the austral summer season of ,2001-2002. The exploration was composed of seven large explosions and 161seismic stations distributed along the 151 km-long seismic line.The first arrival time data are analyzed by a refraction method.It is found that the ice sheet is composed of two layers:the upper layer with P wave velocity of 2.7-2.9 km/s has thickness of 35-45 m,and the lower layer with P wave velocity of 3.7-3.9 km/s continues to the bedrock.Lateral velocity variation in the upper-most crust is revealed:P wave velocity for the upper-most crust in the southern and central parts is 6.1-6.2 km/s and that in the northern part is5.9 km/s. This result implies that the geological boundary observed along the coast in the Lu tzow-Holm Bay and Prince Olav Coast regions possibly continues to the inland area.The S wave velocity is also obtained to be roughly 3.5km/s for the whole upper-most crust.Travel time analysis of two distinct reflection phases shows two horizontal reflecting planes located at 19 and 40km depth; the latter corresponds to the Moho discontinuity

Crustal structure and growth of the Forearc region of Izu-Ogasawara arc

（独）海洋研究開発機構(JAMSTEC)では、2002年から伊豆・小笠原・マリアナ島弧において、大陸地殻の生成過程を明らかにすることを目的に構造調査を進め、現在の島弧地殻のボリュームより多くの玄武岩マグマが必要で島弧地殻を生成する過程でマフィックな島弧地殻の一部をマントル内に戻していること（Takahashi et al., 2007, 2008; Tatsumi et al., 2008）、火山フロントと背弧側の地殻の厚さ分布には相関があり過去のリフティングが検出されたこと（Kodaira et al., 2009）などがわかってきた。前弧域の地殻に関しては、厚い地殻と薄い地殻が存在すること（Takahashi et al., 2011）、地磁気異常から島弧的な構造があること（Yamazaki and Yuasa, 1998）がわかっているが、地殻構造から実証されていなかった。前弧域の地殻構造を求め、地殻進化の影響をどの程度受けているのか、前弧域の島弧成長を明らかにするために、（独）海洋研究開発機構の深海調査船「かいれい」を用いて人工地震探査を行った。 地震探査の測線は、新黒瀬からスミス海脚、第二東鳥島海丘、大町海山を通って、小笠原トラフに至る。得られた速度構造から前弧域は25km程度の地殻の厚い部分と10～15km程度の薄い部分があることが明らかになった。厚い地殻は、北緯32.5度付近、スミス海脚、第二東鳥島海丘、大町海山の下に分布する。新黒瀬側は厚い地殻を持たない。大町海山の内部には異常に厚い下部地殻が分布する。薄い地殻が分布するところでは、堆積層が厚く地殻の厚さの半分近くを占める。大町海山以外の地殻が厚く分布するところでは、P波速度6km/sの速度コンターが上に凸、7km/sの速度コンターが下に凸の形状を示す。火山フロントに沿った地殻構造では、むしろ6km/s以下の速度を持つ層が厚いことが示されている（Kodaira et al., 2007）。これは、前弧域下の島弧地殻は、火山フロント下と比較して未分化な物質を多く含むことを示唆おり、過去の掘削結果とも整合する（e.g., Taylor, 1992）。前弧海盆下の島弧地殻の分布は、地磁気異常の空間分布（Yamazaki and Yuasa, 1998）とよく合致する。新黒瀬周辺で見られる地磁気異常は、本研究から明らかになった地殻が薄く地殻全体が盛り上がっている形状と合致する。伊豆小笠原島弧の本州弧への衝突が新黒瀬の浅海部を作っているものと示唆される。SCG66-03発表要旨 / 日本地球惑星科学連合2012年大会（2012年5月20日～5月25日, 幕張メッセ国際会議場） / 日本惑星科学連合の許諾に基づき本文ファイルを掲

構造研究に基づく南海トラフ（西部）地震発生帯のプレート形状および速度構造の3次元モデル

Great interplate earthquakes have repeatedly occurred in pairs along the Nankai Trough. In order to reduce a great deal of damage to coastal area from both strong ground motion and tsunami generation, it is necessary to understand rupture synchronization and segmentation of the Nankai megathrust earthquake. For a precise estimate of the rupture zone of the Nankai megathrust event based on the knowledge of realistic earthquake cycles and variations of magnitude, it is important to know the geometry and property of the plate boundary of the subduction seismogenic zone. To improve a physical model of the Nankai Trough seismogenic zone, the large-scale high-resolution wide-angle and reflection (MCS) seismic studies, and long-term observation have been conducted since 2008. Marine active source seismic data have been acquired along grid two-dimensional profiles having the total length of ~800km per year. A three-dimensional seismic tomography using active and passive seismic data observed both land and ocean bottom stations have been also performed. This study is part of 'Research concerning Interaction Between the Tokai, Tonankai and Nankai Earthquakes' funded by Ministry of Education, Culture, Sports, Science and Technology, Japan. The seismic survey was conducted off the Tokai area including the onshore survey across the eastern Kii Peninsula in 2012, the final year of this project. Compiling those studies provides a three-dimensional plate geometry and velocity structure models of the western Nankai Trough at the moment. Although their reliability and resolution should be evaluated, these models can be applied to a numerical simulation to examine if the observed rupture zone of the historical event can be reproduced. We will also try to construct more fine-scale model for the entire Nankai Trough area.SSS31-P15ポスター要旨 / 日本地球惑星科学連合2013年大会（2013年5月19日～5月24日, 幕張メッセ国際会議場） / 日本惑星科学連合の許諾に基づき本文ファイルを掲載http://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr10-11/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr11-09/

Structural variation in the incoming Philippine Sea plate along the southwestern Nankai Trough

B32-08発表要旨, 日本地震学会2014年度秋季大会（2014年11月24日～26日, 新潟県新潟市）http://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr14-05/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky14-07/

Structural variation in the incoming Philippine Sea plate along the Nankai Trough

The next large-thrust earthquake along the Nankai Trough, southwest Japan is concerned to occur within this century. Nonvolcanic deep low-frequency tremors and earthquakes are observed around the down-dip limit of the coseismic rupture zone of the last Tonankai and Nankai earthquakes [Obara, 2002]. One of the causes of these low-frequency seismic phenomena is considered to be fluid generated by dehydration processes from the subducting slab. It is important to investigate structural variation in the incoming Philippine Sea plate, including its fluid content to understand the generation of the low-frequency seismic phenomena as well as large-thrust earthquakes. In 2014, we conducted the seismic refraction and reflection survey in the northern margin of the Shikoku Basin, where the Philippine Sea plate is subducting beneath the Eurasia plate at the Nankai Trough. We conducted a 360km long seismic profile about 50-60km seaward of the deformation front along the Nankai Trough. 35 OBSs were deployed along the profile with the interval of 10km. A tuned airgun array shot with a total volume of 7800 cu. in. every 200m for OBSs, and 380 cu. in. every 37.5m for a 192-channel, 1.2km-long hydrophone streamer. In the time-migrated reflection section, variation in the sedimentary layer and basement reflection can be recognized off Shikoku, which may correspond with the boundary of the plate age proposed by magnetic lineation [Okino et al., 1999]. In the southwestern part of the profile, the basement reflection is not always clear, and shows smooth structure. Comparatively in the northeastern part, basement changes in depth drastically with prominent reflection signals. In the wide-angle OBS data, PS converted waves are clearly observed over along the seismic profile. In particular, PS converted waves refracted from the uppermost mantle can be remarkably recognized in the northeastern half of the profile. We will show the structural variation of the oceanic crust of the incoming plate, which may be related to the formation of the Shikoku Basin as well as the generation of the various seismic activities including the low-frequency events, by using OBS data. This study is part of ‘Research project for compound disaster mitigation on the great earthquakes and tsunamis around the Nankai Trough region’ funded by MEXT, Japan.Poster abstract T51A-4578 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec.http://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr14-05/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky14-07/