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81.
Hemendra Acharya 《Natural Hazards》1989,1(4):341-348
A general approach for the estimation of tsunami height and hazard in the vicinity of active volcanoes has been developed. An empirical relationship has been developed to estimate the height of the tsunami generated for an eruption of a given size. This relationship can be used to estimate the tsunami hazard based on the frequency of eruptive activity of a particular volcano. This technique is then applied to the estimation of tsunami hazard from the eruption of the Augustine volcano in Alaska. Modification of this approach to account for a less than satisfactory data base and differing volcanic characteristics is also discussed with the case of the Augustine volcano as an example. This approach can be used elsewhere with only slight modifications and, for the first time, provides a technique to estimate tsunami hazard from volcanic activity, similar to a well-established approach for the estimation of tsunami hazard from earthquake activity. 相似文献
82.
本文介绍了两种离心式泥浆净化设备——NL-227型离心除泥器和WL-230型连续除泥离心机的结构、特点和应用效果,讨论了几种净化设备的分离物的粒度分布. 相似文献
83.
江苏北部开敞淤泥质海岸的侵蚀过程及防护 总被引:9,自引:0,他引:9
开敞淤泥质海岸是淤泥质海岸的主要类型,其自然演变过程,主要受沿海河流泥沙供应条件的制约,一旦泥沙供应消失,海岸往往进入不可逆转的侵蚀过程。江苏北部淤泥质海岸的侵蚀过程,起自1855年黄河入海口北归利津入海以后,主要是在近岸破波对岸滩物质的冲刷和潮流的输移扩散作用下进行的。通过对淤泥质海岸动力和沉积物性质的认识和概化,对海岸侵蚀过程作出定量模拟,并对该地区海岸防护工程作出评价和讨论。 相似文献
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87.
We describe in detail the deformation structures and textures of a large-scale landslide body that developed in the Betto-dani
Valley in northern central Japan. We studied the shape-preferred orientation of clasts and clay flakes and the development
of internal shear planes within the slip zone of the landslide. The slip has an average rate of 5–10 cm/year under the overburden
pressure of approximately 1.6 MPa; these values are similar to those of the proto-decollement zone of the Nankai accretionary
prism in SW Japan. The anisotropy of magnetic susceptibility of samples obtained from the slip zone reveals that the long
axes of clay flakes define an imbricate structure. The slip was due to a long-term periodical creep, which occurs during the
thaw seasons with an average slip rate of 0.16–0.32 μm/min. During the creep, the long axes of grains including clay flakes
in the slip zone are developed from parallel to perpendicular to the slip direction. The observed textures provide a clue
to elucidate the deformation textures and process in the decollement zone of the Nankai prism. 相似文献
88.
Gilberto Saccorotti Ivan Lokmer Christopher J. Bean Giuseppe Di Grazia Domenico Patan 《Journal of Volcanology and Geothermal Research》2007,160(3-4):340-354
Following the installation of a broadband network on Mt. Etna, sustained Long-Period (LP) activity was recorded accompanying a period of total quiescence and the subsequent onset of the 2004–2005 effusive episode. From about 56000 events detected by an automatic classification procedure, we analyse a subset of about 3000 signals spanning the December 17th, 2003–September 25th, 2004, time interval. LP spectra are characterised by several, unevenly-spaced narrow peaks spanning the 0.5–10 Hz frequency band. These peaks are common to all the recording sites of the network, and different from those associated with tremor signals. Throughout the analysed time interval, LP spectra and waveforms maintain significant similarity, thus indicating the involvement of a non-destructive source process that we interpret in terms of the resonance of a fluid-filled buried cavity. Polarisation analysis indicates radiation from a non-isotropic source involving large amounts of shear. Concurrently with LP signals, recordings from the summit station also depict Very-Long-Period (VLP) pulses whose rectilinear motion points to a region located beneath the summit craters at depths ranging between 800 and 1100 m beneath the surface. Based on a refined repicking of similar waveforms, we obtain robust locations for a selected subset of the most energetic LP events from probabilistic inversion of travel-times calculated for a 3D heterogenous structure. LP sources cluster in a narrow volume located beneath the summit craters, and extending to a maximum depth of ≈ 800 m beneath the surface. No causal relationships are observed between LP, VLP and tremor activities and the onset of the 2004–2005 lava effusions, thus indicating that magmatic overpressure played a limited role in triggering this eruption. These data represent the very first observation of LP and VLP activity at Etna during non-eruptive periods, and open the way to the quantitative modelling of the geometry and dynamics of the shallow plumbing system. 相似文献
89.
Thirty-seven new K–Ar ages from West Maui volcano, Hawai‘i, are used to define the waning stages of shield growth and a brief
episode of postshield volcanism. All but two samples from shield-stage strata have reversed polarity magnetization, so conceivably
the exposed shield is not much older than the Olduvai Normal-Polarity subchron, or about 1.8 Ma. The oldest ages obtained
are in the range 1.9–2.1 Ma but have large analytical error. Shield volcanism ended about 1.35 Ma, and postshield volcanism
followed soon thereafter, persisting until about 1.2 Ma. Exposed shield-stage strata were emplaced at a rate of about 0.001 km3 per year, a rate smaller than historic Hawaiian magmatic rates by a factor of 100. Stratigraphic accumulation rates are similar
to those measured previously at Wai‘anae volcano (O‘ahu) or the upper part of the Mauna Kea shield sequence (Hilo drill core,
Hawai‘i). These rates diminish sharply during the final 0.3–0.5 m.y. of the shield stage. Hawaiian shield volcanoes begin
waning well before their last 0.5 m.y. of life, then end quickly, geologically speaking, if West Maui is representative. 相似文献
90.
ACTIVE system for monitoring volcanic activity: A case study of the Izu-Oshima Volcano,Central Japan
Hisashi Utada Yuji Takahashi Yuichi Morita Takao Koyama Tsuneomi Kagiyama 《Journal of Volcanology and Geothermal Research》2007
A system is proposed for the monitoring of changes in the underground structure of an active volcano over time by applying a transient electromagnetic method. The monitoring system is named ACTIVE, which stands for Array of Controlled Transient-electromagnetics for Imaging Volcano Edifice. The system consists of a transmitter dipole used to generate a controlled transient electromagnetic (EM) field and an array of receivers used to measure the vertical component of the transient magnetic field at various distances, with automatic operation of both units. In order to verify the performance of the proposed system, numerical and field experiments were carried out by application of the system to the Izu-Oshima volcano, where a remarkable change in the apparent DC resistivity over time had been detected in association with the eruption in 1986. 相似文献