Endogenous growth of a Miocene submarine dacite cryptodome, Rebun Island, Hokkaido, Japan     

Yoshihiko Goto  Jocelyn McPhie   《Journal of Volcanology and Geothermal Research》1998,84(3-4)

Momo-iwa, Rebun Island, Hokkaido, Japan, is a dacite cryptodome 200–300 m across and 190 m high. The dome is inferred to have intruded wet, poorly consolidated sediment in a shallow marine environment. The internal structure of the dome is concentric, with a massive core, banded rim, and narrow brecciated border, all of which are composed of compositionally uniform feldspar-phyric dacite. Boundaries between each of the zones are distinct but gradational. The massive core consists of homogeneous coherent (unfractured) dacite and is characterized by radial columnar joints 60–200 cm across. The banded rim encircles the massive core and is 40 m wide. It is characterized by large-scale flow banding parallel to the dome surface. The flow banding comprises alternating partly crystalline and more glassy bands 80–150 cm thick. The outermost brecciated border is up to 80 cm thick, and consists of in situ breccia and blocky peperite. The in situ breccia comprises polyhedral dacite clasts 5–20 cm across and a cogenetic granular matrix. The blocky peperite consists of polyhedral dacite clasts 0.5–2 cm across separated by the host sediment (mudstone). The internal structures of the dome suggest endogenous growth involving a continuous magma supply during a single intrusive phase and simple expansion from the interior. Although much larger, the internal structures of Momo-iwa closely resemble those of lobes in subaqueous felsic lobe-hyaloclastite lavas.  相似文献   

Redeposition of volcaniclastic sediments by a tsunami 4600 years ago at Kushima City,south-eastern Kyushu,Japan     

Masaki Yamada  Shigehiro Fujino  Takashi Chiba  Kazuhisa Goto  James Goff 《Sedimentology》2020,67(3):1354-1372

The Hyuga-nada Sea, south-eastern Kyushu, Japan, is located between a strong (Nankai Trough) and a weak interplate coupling zone (Ryukyu Trench). Over the past 400 years this area has only experienced Magnitude 7·5 earthquakes or smaller and associated small-scale tsunamis. However, this short historical record most likely does not include the full range of high magnitude, low frequency giant earthquakes that might have occurred in the region. Thus, it is still unclear whether giant earthquakes and their associated tsunamis have occurred in this region. This paper reports on a prehistoric tsunami deposit discovered in a coastal lowland in south-eastern Kyushu facing the Hyuga-nada Sea. There is a reddish-brown pumiceous layer preserved in a non-marine, organic-rich mud sequence obtained from onshore sediment cores. This layer is recognized as the ca 4600 year old Kirishima-Miike tephra (that is now placed around 4500 years ago) sourced from Mount Kirishima, southern Kyushu. Another whitish pumiceous layer is evident below the Kirishima-Miike tephra in almost all of the sediment cores. A relatively high percentage of marine and brackish diatoms is recorded within this lower pumiceous layer (but not in the surrounding muds or in the overlying Kirishima-Miike tephra), indicating a marine or beach sediment source. Plant material obtained from organic-rich mud immediately below the event layer was dated to ca 4430 to 4710 cal yr bp , providing a limiting-maximum age for this marine incursion event. The presence of marine diatoms below the event layer is probably explained by pre-seismic subsidence. An absence of the resting spore of the planktonic brackish diatom Cheatoceros and the appearance of the freshwater diatom Eunotia serra immediately above the event layer probably represents a marked change to a relatively low-salinity environment. Assuming that there were no significant local geomorphological changes, such as drainage obstruction caused by formation of a new barrier spit, it is considered that co-seismic or immediate post-seismic uplift are the most likely explanations for this notable environmental change. Based on the crustal movements noted before and after the marine incursion, this event is interpreted here as an earthquake-generated tsunami. Moreover, because of these notable seismic crustal movements the tsunamigenic earthquake probably occurred immediately offshore of the study site.  相似文献   

Field-based description of near-surface crustal deformation in a high-strain shear zone: A case study in southern Kyushu,Japan     

Masakazu Niwa  Koji Shimada  Shuji Terusawa  Akira Goto  Nariaki Nishiyama  Toru Nakajima  Takanori Ishihara  Hiroaki Hakoiwa 《Island Arc》2024,33(1):e12516

This study investigated geological evidence for near-surface crustal deformation in a high-strain shear zone that has been geodetically identified but which is not associated with obvious tectonic landforms. Fieldwork was conducted in the east–west-trending southern Kyushu high-strain shear zone (SKHZ), Japan, focusing mainly on occurrences of fracture zones, which are defined by a visible fracture density of >1 per 10 cm² and are commonly associated with cataclasite, fault breccia, and gouge. The area in which east–west-trending fracture zones are dominant is restricted to the east–west-trending, ~2-km-wide aftershock area of the 1997 Northwestern Kagoshima Earthquakes. Analysis of slip data from minor faults using the multiple inverse method, irrespective of whether the faults are in fracture zones, reveals that the area where the calculated main stress field is consistent with the current stress field estimated from focal-mechanism solutions of microearthquakes is restricted to the east–west-trending aftershock area. This finding for the SKHZ contrasts with the case of the Niigata–Kobe Tectonic Zone, which is a major strain-concentration zone with many exposed active faults in central Japan and for which the stress field estimated using fault-slip data is considered to be uniform and coincides with the current stress field. The cumulative amount of displacement estimated from the areal density of fracture zones in the SKHZ study area is smaller than that estimated from geodetically measured strain rates. Investigations based on slip data from minor faults and fracture-zone occurrence could help to identify concealed faults that are too small to generate tectonic landforms but which are sufficiently large to trigger major earthquakes.  相似文献   

A catalogue of local E+A (post-starburst) galaxies selected from the Sloan Digital Sky Survey Data Release 5     

Tomotsugu Goto 《Monthly notices of the Royal Astronomical Society》2007,381(1):187-193

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Evolution of the colour–radius and morphology–radius relations in SDSS galaxy clusters     

Tomotsugu Goto †  Masafumi Yagi  Masayuki Tanaka  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2004,348(2):515-518

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Distribution, origin and transport process of boulders deposited by the 2004 Indian Ocean tsunami at Pakarang Cape, Thailand     

Kazuhisa Goto  Suchana A. Chavanich 《Sedimentary Geology》2007,202(4):821-837

The tsunami of 2004 in the Indian Ocean transported thousands of meters-long boulders shoreward at Pakarang Cape, Thailand. We investigated size, position and long axis orientation of 467 boulders at the cape. Most of boulders found at the cape are well rounded, ellipsoid in shape, without sharp broken edges. They were fragments of reef rocks and their sizes were estimated to be < 14m³ (22.7t). The distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves. It was found that there is no clear evidence indicating monotonous fine/coarse shoreward trends of these boulders along each transect line. On the other hand, the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval. This distribution pattern may suggest that long-lasting oscillatory flows might have repositioned the boulders and separated the big ones from small. No boulders were found on land, indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope. We further conducted numerical calculation of tsunami inundation at Pakarang Cape. According to the calculation, the sea receded and the major part of the tidal bench (area with boulders at present) was exposed above the sea surface before the arrival of the first tsunami wave. The first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation, and then inundated inlands. Our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan-like shape on the tidal bench. The critical wave velocities necessary to move the largest and average-size boulders by sliding can be estimated to be approximately 3.2 and 2.0m/s, respectively. The numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m/s between the reef edge and approximately 500m further offshore. This range is large enough for moving even the largest boulder shoreward. These suggest that the tsunami waves that were directed eastward, struck the reef rocks and coral colonies, originally located on the shallow sea bottom near the reef edge, and detached and transported the boulders shoreward.  相似文献   

Changes in inferred spawning areas of Todarodes pacificus (Cephalopoda: Ommastrephidae) due to changing environmental conditions   总被引：5，自引：0，他引：5  

Sakurai  Y.; Kiyofuji  H.; Saitoh  S.; Goto  T.; Hiyama  Y. 《ICES Journal of Marine Science》2000,57(1):24-30

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The Structure of Young Stellar Jets and Winds Revealed by High Resolution [Fe II] λ1.644μm Line Observations     

Tae-Soo Pyo  Masahiko Hayashi  Naoto Kobayashi  Alan T. Tokunaga  Hiroshi Terada  Miwa Goto  Takuya Yamashita  Yoichi Itoh  Hideki Takami  Naruhisa Takato  Yutaka Hayano  Wolfgang Gaessler  Yukiko Kamata  Yosuke Minowa  Masanori Iye 《Astrophysics and Space Science》2003,287(1-4):21-24

We present high angular resolution spectra taken along the jets from L1551 IRS 5 and DG Tau obtained with the Subaru Telescope. The position-velocity diagrams of the [Fe II] λ 1.644 μmemission line revealed remarkably similar characteristics for the two sources, showing two distinct velocity components separated from each other in both velocity and space with the entire emission range blueshifted with respect to the stellar velocity. The high velocity component (HVC) has a velocity of –200 ––300 km s^-1 with a narrow line width, while the low velocity component (LVC) is around –100 km s^-1 exhibitinig a broad line width. The HVC is located farther away from the origin and is more extended than the LVC. Our results suggest that the HVC is a well-collimated jet originating from the region close to the star, while the LVC is a widely-opened wind accelerated in the region near the inner edge of the accretion disk.  相似文献   

Erratum: Are passive spiral galaxies truly 'passive' and 'spiral'? A near-infrared perspective     

Chisato Yamauchi  Tomotsugu Goto 《Monthly notices of the Royal Astronomical Society》2004,354(4):1280-1280

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Coupled Simulation of Seismic Wave Propagation and Failure Phenomena by Use of an MPS Method     

Junichi Takekawa  Hitoshi Mikada  Tada-nori Goto  Yoshinori Sanada  Yuzuru Ashida 《Pure and Applied Geophysics》2013,170(4):561-570

The failure of brittle materials, for example glasses and rock masses, is commonly observed to be discontinuous. It is, however, difficult to simulate these phenomena by use of conventional numerical simulation methods, for example the finite difference method or the finite element method, because of the presence of computational grids or elements artificially introduced before the simulation. It is, therefore, important for research on such discontinuous failures in science and engineering to analyze the phenomena seamlessly. This study deals with the coupled simulation of elastic wave propagation and failure phenomena by use of a moving particle semi-implicit (MPS) method. It is simple to model the objects of analysis because no grid or lattice structure is necessary. In addition, lack of a grid or lattice structure makes it simple to simulate large deformations and failure phenomena at the same time. We first compare analytical and MPS solutions by use of Lamb’s problem with different offset distances, material properties, and source frequencies. Our results show that analytical and numerical seismograms are in good agreement with each other for 20 particles in a minimum wavelength. Finally, we focus our attention on the Hopkinson effect as an example of failure induced by elastic wave propagation. In the application of the MPS, the algorithm is basically the same as in the previous calculation except for the introduction of a failure criterion. The failure criterion applied in this study is that particle connectivity must be disconnected when the distance between the particles exceeds a failure threshold. We applied the developed algorithm to a suspended specimen that was modeled as a long bar consisting of thousands of particles. A compressional wave in the bar is generated by an abrupt pressure change on one edge. The compressional wave propagates along the interior of the specimen and is visualized clearly. At the other end of the bar, the spalling of the bar is reproduced numerically, and a broken piece of the bar is formed and falls away from the main body of the bar. Consequently, these results show that the MPS method effectively reproduces wave propagation and failure phenomena at the same time.  相似文献