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11.
A seismological overview of long-period ground motion 总被引：1，自引：1，他引：0
Long-period ground motion has become an increasingly important consideration because of the recent rapid increase in the number
of large-scale structures, such as high-rise buildings and oil storage tanks. Large subduction-zone earthquakes and moderate
to large crustal earthquakes can generate far-source long-period ground motions in distant sedimentary basins with the help
of path effects. Near-fault long-period ground motions are generated, for the most part, by the source effects of forward
rupture directivity. Far-source long-period ground motions consist primarily of surface waves with longer durations than near-fault
long-period ground motions. They were first recognized in the seismograms of the 1968 Tokachi-oki and 1966 Parkfield earthquakes,
and their identification has been applied to the 1964 Niigata earthquake and earlier earthquakes. Even if there is no seismogram,
we can identify far-source long-period ground motions through the investigation of tank damage by liquid sloshing. 相似文献
12.
Tetsuichi TAKAGI Sang–Mo KOH Moon–Young KIM Kazuki NAITO Sadahisa SUDO 《Resource Geology》2000,50(4):243-256
Abstract: The Milyang pyrophyllite deposit, which is embedded in the Late Cretaceous Yuchon Group of the Kyongsang Supergroup, is one of the largest hydrothermal clay deposits in the Kyongsang basin, southeast Korea. Host rocks of the deposit are porphyritic andesite lava and minor andesitic lapilli tuff. In the Milyang district, a hydrothermally altered zone is about 2 × 3 km in extent; we can recognize the concentric arrangement of advanced argillic, propylitic, and sericitic alteration zones from the central to peripheral parts of the zone. The Milyang pyrophyllite deposit forms a part of the advanced argillic alteration zone. The Milyang pyrophyllite deposit is subdivided into the following four zones based on mineral assemblages: the pyrophyllite zones 1, 2, 3, and the silicified zone. The pyrophyllite zone 1, which occupies the central part of the deposit, comprises mainly pyrophyllite, kaolinite, and diaspore without quartz. Diaspore nodules often concentrate in beds 40–50 cm thick. Andalusite, dumortierite, and tourmaline locally occur as network veins, crack‐filler, or small spherulitic spots. The Al2O3 content of the ore ranges from 27 to 36 wt%. The pyrophyllite zone 2, which constitutes a major part of the deposit, comprises mainly pyrophyllite, kaolinite, and quartz. The Al2O3 content of the ore ranges from 15 to 24 wt%. The pyro‐phyllite zone 3 is the hematite‐rich marginal facies of the deposit. The silicified zone, which occurs as beds and septa, is mostly composed of quartz with minor pyrophyllite and kaolinite; the SiO2 contents range from 79 to 90 wt%. Comparing chemical compositions of the high‐Al ores with those of unaltered host andesite, the Fe, Ca, alkalis, HFSE, and HREE contents are significantly depleted, whereas S, B, As, Sr, and LREE are enriched. The hydrothermal alteration of the Milyang pyrophyllite deposit can be classified into the following four stages: 1) extensive sericitic and propylitic alteration, 2) medium‐temperature (200–250°C) advanced argillic alteration, 3) high‐temperature (250–350°C or more) advanced argillic alteration, and 4) retrograde low‐temperature alteration. The heat and some volatile components such as B and S would be derived from the Pulguksa Granite intruded underneath the deposit. 相似文献
13.
Marvin Lüpke Michael Leuchner Delphis Levia Kazuki Nanko Shin'ichi Iida Annette Menzel 《水文研究》2019,33(26):3391-3406
Forest canopies present irregular surfaces that alter both the quantity and spatiotemporal variability of precipitation inputs. The drop size distribution (DSD) of rainfall varies with rainfall event characteristics and is altered substantially by the forest stand properties. Yet, the influence of two major European tree species, European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst), on throughfall DSD is largely unknown. In order to assess the impact of these two species with differing canopy structures on throughfall DSD, two optical disdrometers, one above and one below the canopy of each European beech and Norway spruce, measured DSD of both incident rainfall and throughfall over 2 months at a 10‐s resolution. Fractions of different throughfall categories were analysed for single‐precipitation events of different intensities. While penetrating the canopies, clear shifts in drop size and temporal distributions of incoming rainfall were observed. Beech and spruce, however, had different DSD, behaved differently in their effect on diameter volume percentiles as well as width of drop spectrum. The maximum drop sizes under beech were higher than under spruce. The mean ± standard deviation of the median volume drops size (D50) over all rain events was 2.7 ± 0.28 mm for beech and 0.80 ± 0.04 mm for spruce, respectively. In general, there was a high‐DSD variability within events indicating varying amounts of the different throughfall fractions. These findings help to better understand the effects of different tree species on rainfall partitioning processes and small‐scale variations in subcanopy rainfall inputs, thereby demonstrating the need for further research in high‐resolution spatial and temporal properties of rainfall and throughfall. 相似文献
14.
Teleseismic and strong-motion data are inverted to determine the rupture process during the November 1999 Düzce earthquake in NW Turkey. The fault geometry, rise time and rupture velocity are determined from the aftershock distribution and preliminary inversions of the teleseismic data. Joint inversion of the teleseismic and strong-motion data is then carried out for the slip distribution. We obtain the strike 264°, dip 64°, rake −172°, seismic moment 5.0×1019 N m (Mw 7.1), and average stress drop 7 MPa. This earthquake was characterized by bilateral fault rupture and asymmetric slip distribution. Two asperities (areas of large slip) are identified, the eastern one being 1.5 times larger than the western one. The derived slip distribution is consistent with the aftershock distribution, surface rupture and damage. The point of rupture initiation in this Düzce earthquake coincided with the eastern tip of the aftershock distribution of the August 1999 Izmit earthquake. 相似文献
15.
Kazuki Kohketsu 《Geophysical Journal International》1987,89(3):821-838
Summary. The reflectivity method for complete SH seismograms has been extended to two-dimensionally layered structures. The Aki-Larner technique is generalized to solve the integral equations for 2-D boundary conditions, and propagator matrices are enlarged to express a total SH wavefield. Synthetic seismograms in a soft basin are calculated for an incident plane-wave. They compare favourably with the results of the finite-element and finite-difference methods even in the later portion where asymptotic ray and beam theories break down. Synthetic seismograms due to a line force and a point dislocation are also presented. 相似文献
16.
Kazuki Koketsu 《Journal of Seismology》2016,20(4):1131-1150
We reviewed joint inversion studies of the rupture processes of significant earthquakes, using the definition of a joint inversion in earthquake source imaging as a source inversion of multiple kinds of datasets (waveform, geodetic, or tsunami). Yoshida and Koketsu (Geophys J Int 103:355–362, 1990), and Wald and Heaton (Bull Seismol Soc Am 84:668–691, 1994) independently initiated joint inversion methods, finding that joint inversion provides more reliable rupture process models than single-dataset inversion, leading to an increase of joint inversion studies. A list of these studies was made using the finite-source rupture model database (Mai and Thingbaijam in Seismol Res Lett 85:1348–1357, 2014). Outstanding issues regarding joint inversion were also discussed. 相似文献
17.
The Miocene Kitami rhyolite, consisting of orthopyroxene and plagioclase-phyric lavas and dikes, occurs on the back-arc side of the Kuril arc with coeval basalts and Fe-rich andesites. Temperatures estimated from orthopyroxene–ilmenite pairs exceed 900°C. Although the whole rock compositions of the Kitami rhyolite correspond to S-type granites (i.e., high K, Al, large ion lithophile elements, and low Ca and Sr), Sr–Nd isotope compositions are remarkably primitive, and similar to those of the coeval basalts and andesites. They are distinct from those of lower crustal metamorphic rocks exposed in the area. Comparison of chondrite-normalized rare earth element (REE) patterns between the rhyolite and the basalts and andesites show that the rhyolite is more light REE enriched, but has similar heavy REE contents than the basalts. All rhyolites show negative Eu anomalies. The geochemical data suggest that did not formed by simple dehydration melting of basaltic rocks or fractional crystallization of basaltic magmas. The features of slab-derived fluids expected from recent high pressure experimental studies indicates that mantle wedge is partly metasomatized with “rhyolitic” materials from subducted slabs; it is more likely that very low degree partial melting of the metasomatized mantle wedge formed the rhyolite magma. 相似文献
18.
Richard S. Fiske Katharine V. Cashman Atsushi Shibata Kazuki Watanabe 《Bulletin of Volcanology》1998,59(4):262-275
A new and detailed bathymetric map of the Myojinsho shallow submarine volcano provides a framework to interpret the physical
volcanology of its 1952–1953 eruption, especially how the silicic pyroclasts, both primary and reworked, enlarged the volcano
and were dispersed into the surrounding marine environment. Myojinsho, 420 km south of Tokyo along the Izu–Ogasawara arc,
was the site of approximately 1000 phreatomagmatic explosions during the 12.5-month eruption. These explosions shattered growing
dacite domes, producing dense clasts that immediately sank into the sea; minor amounts of pumice floated on the sea surface
after some of these events. The Myojinsho cone has slopes of almost precisely 21° in the depth range 300–700 m.We interpret
this to be the result of angle-of-repose deposition of submarine pyroclastic gravity flows that traveled downslope in all
directions. Many of these gravity flows resulted from explosions and associated dome collapse, but others were likely triggered
by the remobilization of debris temporarily deposited on the summit and steep upper slopes of the cone. Tephra was repeatedly
carried into air in subaerial eruption columns and fell into the sea within 1–2 km of the volcano's summit, entering water
as deep as 400 m. Because the fall velocity of single particles decreased by a factor of ∼30 in passing from air into the
sea, we expect that the upper part of the water column was repeatedly choked with hyperconcentrations of fallout tephra. Gravitational
instabilities within these tephra-choked regions could have formed vertical density currents that descended at velocities
greater than those of the individual particles they contained. Upon reaching the sea floor, many of these currents probably
continued to move downslope along Myojinsho's submarine slopes. Fine tephra was elutriated from the rubbly summit of the volcano
by upwelling plumes of heated seawater that persisted for the entire duration of the eruption. Ocean currents carried this
tephra to distal areas, where it presumably forms a pyroclastic component of deep-sea sediment.
Received: 5 December 1996 / Accepted: 17 September 1997 相似文献
19.
20.
Md. Aftabuzzaman Kazuki Yomogida Shota Suzuki Hideko Takayanagi Akimasa Ishigaki Shiki Machida Yoshihiro Asahara Koshi Yamamoto Naoto Hirano Shin-Ichi Sano Shun Chiyonobu Davide Bassi Yasufumi Iryu 《Island Arc》2021,30(1):e12400
Sedimentological, geochemical, and chronological analyses were carried out on 18 carbonate rock samples collected at depths of 938, 1085, and 3354 m on the western slope of Minamitorishima (Marcus Island), which is located near the western margin of the Pacific Plate. Four groups of carbonate rocks were distinguished: a mollusk-rich limestone, a coral-rich dolomite, a foraminiferal-nannofossil packstone, and a phosphatized mudstone/wackestone. The mollusk-rich limestone is characterized by the dominance of bivalves (including rudists) and gastropod shells. Strontium isotope ratios (87Sr/86Sr) and Mesorbitolina ex gr. texana (a large benthic foraminifer) indicate that the shallow-water carbonates were deposited during the late Aptian–early Albian (ca. 123–111 Ma). The coral-rich dolomite is characterized by abundant scleractinian corals and nongeniculate coralline algae associated with encrusting acervulinid foraminifers. The biotic composition is similar to that of the Oligocene–Pleistocene carbonates reported from other seamounts in the northwestern Pacific. Geochemical data show that the coral-rich carbonates were dolomitized at 9.5–6.8 Ma (Tortonian–Messinian) and that normal seawater was the most likely parent fluid. The foraminiferal-nannofossil packstone is a semi-consolidated foraminiferal-nannofossil ooze and was deposited during the Pleistocene (0.99–0.45 Ma). The phosphatized mudstone/wackestone is marked by the absence of macrofossils and the presence of traces of planktic foraminifers. Although its depositional age is not constrained, the Sr isotope ratios indicate that the phosphatization occurred at 33.2–28.9 Ma. After the deposition of the Cretaceous shallow-water carbonates, including the mollusk-rich limestone, Minamitorishima was drowned and its top was covered with a pelagic cap, represented by the mudstone/wackestone. The late Eocene–early Oligocene volcanism (40.2–33.2 Ma) caused episodic uplift and returned the top of Minamitorishima to a shallow-water environment. After the early Oligocene phosphatization of the pelagic cap, coral reefs flourished on the top of this island. The reef limestone was dolomitized during the Tortonian–Messinian. 相似文献