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Shinozaki Tetsuya Sawai Yuki Ito Kazumi Hara Junko Matsumoto Dan Tanigawa Koichiro Pilarczyk Jessica E. 《Natural Hazards》2020,103(1):713-730
Geological evidence of recent tsunamis from sediment samples collected from Lake Tokotan, a coastal lagoon in eastern Hokkaido, northern Japan, was detected using computed tomography (CT) and soft X-ray images, grain size, and radionuclide profiles. Initial field observations revealed that sediments had no discernable sedimentary structures at the top of the core. However, results of CT imaging, soft X-ray, and grain size analyses show evidence for three invisible sand layers that are intercalated with mud layers. These sand layers exhibit trends of landward fining and thinning. Furthermore, the distribution of sand layers was limited to the center and seaward parts of the lake. Vertical profiles of cesium and lead concentrations in combination with recent eyewitness accounts indicated that these sand layers are correlated with the 1973 Nemuro-oki, 1960 Chilean, and 1952 Tokachi-oki tsunami events. The deeper part of the sediment cores includes three volcanic ash layers and three prehistoric coarse sand layers. The prehistoric layers are correlated with unusually large tsunamis that were geologically identified in previous studies from eastern Hokkaido. These findings suggest that nondestructive techniques, in combination with radionuclide analysis, allow for detection of frequent but faint tsunami deposits. This technique allows for an improved understanding of the history of tsunami inundation in Lake Tokotan and of other locations for which stratigraphic evidence for faint tsunamis layers is not readily apparent from field assessments.
相似文献2.
Tsunami deposit associated with the 2011 Tohoku‐oki tsunami in the Hasunuma site of the Kujukuri coastal plain,Japan 
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下载免费PDF全文 Dan Matsumoto Yuki Sawai Koichiro Tanigawa Osamu Fujiwara Yuichi Namegaya Masanobu Shishikura Kyoko Kagohara Haruo Kimura 《Island Arc》2016,25(5):369-385
We describe the detailed sedimentary characteristics of a tsunami deposit associated with the 2011 Tohoku‐oki tsunami in Hasunuma, a site on the Kujukuri coastal plain, Japan. The thick tsunami deposit was limited to within 350 m from the coastline whereas the inundation area extended about 1 km from the coastline. The tsunami deposit was sampled by excavation at 29 locations along three transects and studied using peels, soft‐X imaging and grain‐size analysis. The deposit covers the pre‐existing soil and reached a maximum measured thickness of 35 cm. It consists mainly of well‐sorted medium to fine sand. On the basis of sedimentary structures and changes in grain size, we divided the tsunami deposit into several sedimentary units, which may correspond to multiple inundation flows. The numbers of units and their sedimentary features vary among the three transects, despite the similar topography. This variation implies a considerable influence of local effects such as elevation, vegetation, microtopography, and distance from footpaths, on the tsunami‐related sedimentation. 相似文献
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When protoplanets growing by accretion of planetesimals have atmospheres, small planetesimals approaching the protoplanets lose their energy by gas drag from the atmospheres, which leads them to be captured within the Hill sphere of the protoplanets. As a result, growth rates of the protoplanets are enhanced. In order to study the effect of an atmosphere on planetary growth rates, we performed numerical integration of orbits of planetesimals for a wide range of orbital elements and obtained the effective accretion rates of planetesimals onto planets that have atmospheres. Numerical results are obtained as a function of planetesimals’ eccentricity, inclination, planet’s radius, and non-dimensional gas-drag parameters which can be expressed by several physical quantities such as the radius of planetesimals and the mass of the protoplanet. Assuming that the radial distribution of the gas density near the surface can be approximated by a power-law, we performed analytic calculation for the loss of planetesimals’ kinetic energy due to gas drag, and confirmed agreement with numerical results. We confirmed that the above approximation of the power-law density distribution is reasonable for accretion rate of protoplanets with 1-10 Earth masses, unless the size of planetesimals is too small. We also calculated the accretion rates of planetesimals averaged over a Rayleigh distribution of eccentricities and inclinations, and derived a semi-analytical formula of accretion rates, which reproduces the numerical results very well. Using the obtained expression of the accretion rate, we examined the growth of protoplanets in nebular gas. We found that the effect of atmospheric gas drag can enhance the growth rate significantly, depending on the size of planetesimals. 相似文献
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Tomoyasu Tanigawa Shinsuke Abe Masateru Ishiguro Tadashi Mukai 《Earth, Moon, and Planets》2010,106(1):55-65
We present two scenarios for production of the Quadrantid stream based on two different models for its origin: the extinct
model in which 2003EH1 was an active comet that released the dust particles during past 5000 years, stopping its activity
abruptly in AD 1488; and the split model; in which a catastrophic disruption of an asteroid at AD 1488 released a large number
of dust particles in a single event. We calculate the orbital evolution of test particles released in both cases and derive
the resulting size distribution of surviving meteoroids in the current Quadrantid stream in the form of s
−α
ds, where s denotes the radius of a meteoroid. We find α = 3.1 in the extinct model and 2.0 in the split model. In addition, the radius
of the surviving meteoroids is derived as s >10 μm in the both models. We propose, based on our estimation of the infrared color ratio for the Quadrantid stream derived
from both models, that infrared observations of the Quadrantid stream may determine which origin model is more reasonable. 相似文献
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Geochemical characteristics of deposits from the 2011 Tohoku‐oki tsunami at Hasunuma,Kujukuri coastal plain,Japan 下载免费PDF全文
下载免费PDF全文 Tetsuya Shinozaki Yuki Sawai Junko Hara Minoru Ikehara Dan Matsumoto Koichiro Tanigawa 《Island Arc》2016,25(5):350-368
We examined the geochemical characteristics and temporal changes of deposits associated with the 2011 Tohoku‐oki tsunami. Stable carbon isotope ratios, biomarkers, and water‐leachable ions were measured in a sandy tsunami deposit and associated soils sampled at Hasunuma, Kujukuri coastal plain, Japan, in 2011 and 2014. At this site, the 2011 tsunami formed a 10–30 cm ‐thick layer of very fine to medium sand. The tsunami deposit was organic‐poor, and no samples contained any detectable biomarkers of either terrigenous or marine origin. In the underlying soil, we identified hydrocarbons and sterols derived from terrestrial plants, but detected no biomarkers of marine origin. In the samples collected in 2011, concentrations of tsunami‐derived water‐leachable ions were highest in the soil immediately beneath the tsunami deposit and then decreased gradually with depth. Because of its finer texture and higher organic content, the soil has a higher water‐holding capacity than the sandy tsunami deposit. This distribution suggests that ions derived from the tsunami quickly penetrated the sand layer and became concentrated in the underlying soil. In the samples collected in 2014, concentrations of water‐leachable ions were very low in both soil and sand. We attribute the decrease in ion concentrations to post‐tsunami rainfall, seepage, and seasonal changes in groundwater level. Although water‐leachable ions derived from seawater were concentrated in the soil beneath the tsunami deposit following the tsunami inundation, they were not retained for more than a few years. To elucidate the behavior of geochemical characteristics associated with tsunamis, further research on organic‐rich muddy deposits (muddy tsunami deposits and soils beneath sandy tsunami deposits) as well as sandy tsunami deposits is required. 相似文献
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We compare various objects as the possible parent comet of the1998 June Boötid, by using the Tisserand invariant and the D-discriminant. Furthermore,in order to investigate the behaviour of the meteoric stream orbit, wesimulate the orbital evolution of test particles that are released from7P/Pons–Winnecke. We show firstly that the parent comet of the 1998 June Boötids, is 7P/Pons–Winnecke, and secondly that the meteoroids which constitute 1998 June Boötids were released in 1819 and 1869 from the parent comet. In themid-1900s the meteoroids started to transfer to Earth-colliding orbitsby Jovian perturbations. 相似文献
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Mechanical response of the south flank of kilauea volcano, hawaii, to intrusive events along the rift systems 总被引：1，自引：0，他引：1
John J. Dvorak Arnold T. Okamura Thomas T. English Robert Y. Koyanagi Jennifer S. Nakata Maurice K. Sako Wilfred T. Tanigawa Kenneth M. Yamashita 《Tectonophysics》1986,124(3-4)
Increased earthquake activity and compression of the south flank of Kilauea volcano, Hawaii, have been recognized by previous investigators to accompany rift intrusions. We further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major rift intrusions which occurred between December 1971 and January 1981. The seismic response of the south flank to individual rift intrusions is immediate; the increased rate of earthquake activity lasts from 1 to 4 weeks. Horizontal strain measurements indicate that compression of the south flank usually accompanies rift intrusions and eruptions. Emplacement of an intrusion at a depth greater than about 4 km, such as the June 1982 southwest rift intrusion, however, results in a slight extension of the subaerial portion of the south flank.Horizontal strain measurements along the south flank are used to locate the January 1983 east-rift intrusion, which resulted in eruptive activity. The intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet. This model suggests that the intrusive body that compressed the south flank in January 1983 extended from the surface to about 2.4 km depth, and was aligned along a strike of N66°E. The intrusion is approximately 11 km in length, extended beyond the January 1983 eruptive fissures, which are 8 km in length and is contained within the 14-km-long region of shallow rift earthquakes. 相似文献
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Takayuki Tanigawa 《Planetary and Space Science》2008,56(13):1758-1763
I review the role of planetary migration on the formation process of terrestrial planets. I first show a simple estimation for growth timescale of solid proto-planets and review a linear theory of disk-planet gravitational interaction to estimate the migration rate of proto-planets in a gas disk, and then discuss the difficulty of the formation of terrestrial planets in terms of comparison between migration timescale and growth timescale. Next I show recent studies which suggest possible mechanisms to solve the problem. I briefly discuss the formation process of Mercury in the context of terrestrial-planet formation. 相似文献
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