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1.
Thurber CH 《Science (New York, N.Y.)》1984,223(4632):165-167
Application of simultaneous inversion of seismic P-wave arrival time data to the investigation of the crust beneath Kilauea Volcano yields a detailed picture of the volcano's heterogeneous structure. Zones of anomalously high seismic velocity are found associated with the volcano's rift zones. A low-velocity zone at shallow depth directly beneath the caldera coincides with an aseismic region interpreted as being the locus of Kilauea's summit magma complex. 相似文献
2.
In April 1979, measurements of nitrogen dioxide in the upper atmosphere were made near Soufriere Volcano by twilight optical-absorption techniques. The derived value of 5 x 10(15) molecules per square centimeter column implies an enhancement of 25 percent over earlier abundances measured in the same latitudinal regions. This enhancement may represent the normal stratospheric variability of nitrogen dioxide in the equatorial region but in any case may be considered an upper limit to the volcano's effect on the total nitrogen dioxide abundance. 相似文献
3.
A magnitude 7.2 earthquake in 1975 caused the south flank of Kilauea Volcano, Hawaii, to move seaward in response to slippage along a deep fault. Since then, a large part of the volcano's edifice has been adjusting to this perturbation. The summit of Kilauea extended at a rate of 0.26 meter per year until 1983, the south flank uplifted more than 0.5 meter, and the axes of both the volcano's rift zones extended and subsided; the summit continues to subside. These ground-surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the rift zones. Kilauea's magmatic system is, therefore, probably deeper and more extensive than previously thought; the summit and both rift zones may be underlain by a thick, near vertical dike-like magma system at a depth of 3 to 9 kilometers. 相似文献
4.
Cataclysmic flooding is a geomorphological process of planetary significance. Landforms of flood origin resulted from late Pleistocene ice-dammed lake failures in the Altay Mountains of south-central Siberia. Peak paleoflows, which exceeded 18 x 10(6) cubic meters per second, are comparable to the largest known terrestrial discharges of freshwater and show a hydrological scaling relation to floods generated by catastrophic dam failures. These seem to have been Earth's greatest floods, based on a variety of reconstructed paleohydraulic parameters. 相似文献
5.
The Soufrière volcano in St. Vincent erupted from October 1971 to March 1972, as 80 x 10(6) m(3) of basaltic andesite lava was quietly extruded inside the mile-wide crater. The eruption was largely subaqueous, taking place in the 180-m-deep crater lake, and resulted in the emergence of a steep-sided island. The mild character of the eruption and the absence of seismic activity stand in direct contrast to the highly explosive character of the eruption of 1902 to 1903. 相似文献
6.
采用线性回归、气候倾向率、积分湿度指标和干湿指标分析辽宁本溪降水趋势变化和旱涝频率及发生时段。结果表明,在近55年里,本溪年降水量倾向率为-30.749mm/10a,趋势减少165mm;植物生长季降水量倾向率为-31.371/10a,趋势减少173mm。气候类型有所转变,由20年前是轻涝型转为湿润型。农业需水满意程度在150%以上,年平均降水盈余290mm;中涝至重涝有10年,约五年一遇;出现轻旱有5年,约十年一遇。春季中旱以下约十年二遇,中涝以上约十年一遇;夏季中涝以上约二年一遇;秋季中涝以上约十年二遇,中旱以下约十年四遇。7、8月重涝出现频率54.5%。5月和9月是干旱发生频率较高时段。 相似文献
7.
Brooks BA Foster J Sandwell D Wolfe CJ Okubo P Poland M Myer D 《Science (New York, N.Y.)》2008,321(5893):1177
We demonstrate that a recent dike intrusion probably triggered a slow fault-slip event (SSE) on Kilauea volcano's mobile south flank. Our analysis combined models of Advanced Land Observing Satellite interferometric dike-intrusion displacement maps with continuous Global Positioning System (GPS) displacement vectors to show that deformation nearly identical to four previous SSEs at Kilauea occurred at far-field sites shortly after the intrusion. We model stress changes because of both secular deformation and the intrusion and find that both would increase the Coulomb failure stress on possible SSE slip surfaces by roughly the same amount. These results, in concert with the observation that none of the previous SSEs at Kilauea was directly preceded by intrusions but rather occurred during times of normal background deformation, suggest that both extrinsic (intrusion-triggering) and intrinsic (secular fault creep) fault processes can lead to SSEs. 相似文献
8.
Hernández PA Notsu K Salazar JM Mori T Natale G Okada H Virgili G Shimoike Y Sato M Pérez NM 《Science (New York, N.Y.)》2001,292(5514):83-86
Magmatic carbon dioxide (CO2) degassing has been documented before the 31 March 2000 eruption of Usu volcano, Hokkaido, Japan. Six months before the eruption, an increase in CO2 flux was detected on the summit caldera, from 120 (September 1998) to 340 metric tons per day (September 1999), followed by a sudden decrease to 39 metric tons per day in June 2000, 3 months after the eruption. The change in CO2 flux and seismic observations suggests that before the eruption, advective processes controlled gas migration toward the surface. The decrease in flux after the eruption at the summit caldera could be due to a rapid release of CO2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera. 相似文献
9.
为评价公路洪灾的风险性,以雅安市为研究对象,基于公路洪灾致灾机理、破坏形态,综合考虑致灾因子、孕灾环境、承灾体和灾情因子四方面因素,遴选出公路造价等11个指标构建公路洪灾风险评估指标体系.利用层次分析法、模糊概率理论建立公路洪灾风险评估模型,对雅安市公路洪灾风险进行区划.区划结果表明:雅安市公路洪灾风险性被分为高中风险亚区、中高风险亚区和中低风险亚区、低风险区四档三级.经济发达的雨城区的公路洪灾风险性较高,名山及西南部区县次之,宝兴、芦山的公路洪灾风险性较小;分区结果与近三年公路洪灾损失结果相符,评价结果有一定的科学性和参考价值. 相似文献
10.
Renne PR Ernesto M Pacca IG Coe RS Glen JM Prévot M Perrin M 《Science (New York, N.Y.)》1992,258(5084):975-979
The Paraná-Etendeka flood volcanic event produced approximately 1.5 x 10(6) cubic kilometers of volcanic rocks, ranging from basalts to rhyolites, before the separation of South America and Africa during the Cretaceous period. New (40)Ar/(39)Ar data combined with earlier paleomagnetic results indicate that Paraná flood volcanism in southern Brazil began at 133 +/- 1 million years ago and lasted less than 1 million years. The implied mean eruption rate on the order of 1.5 cubic kilometers per year is consistent with a mantle plume origin for the event and is comparable to eruption rates determined for other well-documented continental flood volcanic events. Paraná flood volcanism occurred before the initiation of sea floor spreading in the South Atlantic and was probably precipitated by uplift and weakening of the lithosphere by the Tristan da Cunha plume. The Parana event postdates most current estimates for the age of the faunal mass extinction associated with the Jurassic-Cretaceous boundary. 相似文献
11.
通过对东北地区夏季旱涝及低温冷害对农业生产影响的研究，确立了在山区及平原地区旱涝、年度低温冷害发生的指标以及减产幅度。利用VB6.0编程语言和AUTHORWARE多媒体软件建成了东北夏季旱涝及低温冷害对农业生产影响评价系统和防御服务系统。该系统可利用预报气象信息对旱涝和低温冷害发生程度进行了预测和评价。 相似文献
12.
Williams SN Lowe DR Stoiber RE Gemmell JB Connor CB P NG C AL 《Science (New York, N.Y.)》1986,233(4767):964-967
The 13 November 1985 eruption of Nevado del Ruiz volcano, in Colombia, released a small volume of pyroclastic material and a disproportionately large volume of volcanic gas. Before the eruption, summit fumarole gases became less water-rich, and the sulfur/chlorine ratio increased. Remote measurements of sulfur dioxide flux after the eruption indicated active degassing at levels associated with eruptive or inter-eruptive stages of other volcanoes. Thermal water analyses revealed increases in magnesium, calcium, and potassium and an increase in the magnesium/chlorine ratio, suggesting that these elements may have been leached from new magma. Ash leachate data showed sulfate and chloride concentrations and ratios that would be expected for the late stages ofa major Plinian eruption. Water from the lahar contained high concentrations of sulfate and had a sulfur/chlorine ratio of 4.67, suggesting that water ejected from the crater lake and turbulent mixing of pyroclasts and glacial ice triggered the lahar. Microprobe analyses of pumice from this eruption and the most recent previous event showed similar mixed andesites. The uniform composition of the pumices and the unusually high ratio of gas to magma suggest that, although a new batch of magma triggered this eruption, the pumice that erupted may actually be old. Large volumes of new magma and glacial ice make the volcano dangerous and should stimulate development of an integrated long-term monitoring program to include Tolima volcano, 25 kilometers to the south. 相似文献
13.
基于信息扩散理论的暴雨洪涝风险分析 总被引：1，自引：0，他引：1
运用信息扩散理论分析方法,对益阳市51年的暴雨洪涝进行了风险分析。结果表明,日降水量为50～70 mm的暴雨风险水平全市基本上不存在空间差异,出现机率在50%以上,日降水量≥80 mm的暴雨空间分布不均,日降水量≥200 mm出现机率较小;年暴雨日数≤9 d时湖区风险高于山区,≥10 d时山区风险水平较高;年最大10 d降水量引起的重度洪涝山区的风险重于湖区;4～9月降水过多引发的洪涝风险安化最明显,轻度和中度洪涝均为4年一遇,重度洪涝为7年一遇;4～6月降水过多引发的洪涝主要为轻度和中度洪涝,且多出现在湖区。 相似文献
14.
Leifer R Hinchliffe L Fisenne I Franklin H Knutson E Olden M Sedlacek W Mroz E Cahill T 《Science (New York, N.Y.)》1981,214(4523):904-907
Gas measurements made in the stratospheric plume from the eruption of Mount St. Helens on 18 May 1980 were not consistent with a reported large injection of radon-222 into the atmosphere. No enrichment in the volatile element polonium was found in filter samples, and the ratio of polonium-210 to lead-210 was not different from background values. Data obtained with an experimental impactor, flown shortly after the eruption, showed an increase of 10(3) in the stratospheric number concentration of submicrometer sulfate particles compared to concentrations before the eruption. 相似文献
15.
The injection into the stratosphere of large quantities of sulfur during the June 1991 eruption of Mount Pinatubo (Philippines) and the subsequent formation of sulfate aerosol particles have generated a number of perturbations in the atmosphere with potential effects on the Earth's climate. Changes in the solar and infrared radiation budget caused by the eruption should produce a cooling of the troposphere and a warming of the lower stratosphere. These changes could affect atmospheric circulation. In addition, heterogeneous chemical reactions on the surface of sulfate aerosol particles render the ozone molecules more vulnerable to atmospheric chlorine and hence to man-made chlorofluorocarbons. 相似文献
16.
The great tambora eruption in 1815 and its aftermath 总被引：1，自引：0，他引：1
Stothers RB 《Science (New York, N.Y.)》1984,224(4654):1191-1198
Quantitative analytical methods are used to reconstruct the course of events during and after the cataclysmic eruption of Mount Tambora, Indonesia, on 10 and 11 April 1815. This was the world's greatest ash eruption (so far as is definitely known) since the end of the last Ice Age. This synthesis is based on data and methods from the fields of volcanology, oceanography, glaciology, meteorology, climatology, astronomy, and history. 相似文献
17.
云南蒋家沟上游重力侵蚀和支沟泥石流形成的研究 总被引：1，自引：0，他引：1
通过对云南蒋家沟流域上游泥石流形成源区的长时间雨季观测,分析了短历时暴雨条件下沟岸坡体的重力侵蚀过程以及上游支沟泥石流的形成过程。结果表明:尽管蒋家沟源区沟岸坡体坡度较大,但由于土体密实,且大部分处于非饱和状态,受基质吸力的影响,土体强度较高,坡体整体是稳定的。降雨过程中,由于短历时暴雨的降水入渗只能影响坡体表层的含水量,对坡体的整体稳定性影响较小;上游支沟中的洪水和泥石流冲刷坡脚、掏蚀沟床产生了大量的滑塌,是上游沟岸坡体重力侵蚀的主要方式,重力侵蚀使得原来密实的沟岸坡体变得松散,强度大大降低,为泥石流的暴发提供了固体物质基础。在暴雨过程中,这些松散堆积物饱和并在其自身重力和沟道径流的作用下启动,形成上游的支沟泥石流。 相似文献
18.
Waitt RB Pierson TC Macleod NS Janda RJ Voight B Holcomb RT 《Science (New York, N.Y.)》1983,221(4618):1394-1397
An explosive eruption of Mount St. Helens on 19 March 1982 had substantial impact beyond the vent because hot eruption products interacted with a thick snowpack. A blast of hot pumice, dome rocks, and gas dislodged crater-wall snow that avalanched through the crater and down the north flank. Snow in the crater swiftly melted to form a transient lake, from which a destructive flood and lahar swept down the north flank and the North Fork Toutle River. 相似文献
19.
Sigurdsson H 《Science (New York, N.Y.)》1982,216(4550):1106-1108
The explosive phase of the 1979 Soufriere eruption produced 37.5 x 10(6) cubic meters (dense-rock equivalent) of tephra, consisting of about 40 percent juvenile basaltic andesite and 60 percent of a nonjuvenile component derived from the fragmentation of the 1971-1972 lava island during phreatomagmatic explosions. The unusually fine grain size, poor sorting, and bimodality of the land deposit are attributed to particle aggregation and the formation of accretionary lapilli in a wet eruption column. 相似文献
20.
During an eruption of the Alaskan volcano Mount St. Augustine in the spring of 1986, there was concern about the possibility that a tsunami might be generated by the collapse of a portion of the volcano into the shallow water of Cook Inlet. A similar edifice collapse of the volcano and ensuing sea wave occurred during an eruption in 1883. Other sea waves resulting in great loss of life and property have been generated by the eruption of coastal volcanos around the world. Although Mount St. Augustine remained intact during this eruptive cycle, a possible recurrence of the 1883 events spurred a numerical simulation of the 1883 sea wave. This simulation, which yielded a forecast of potential wave heights and travel times, was based on a method that could be applied generally to other coastal volcanos. 相似文献