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91.
水泄铜钴矿区地质条件较为复杂,控矿因素较多,通过分析认为主要受断层及岩性控制,地层初始富集,构造及区域变质作用提供通道及热源。水的循环、溶解作用形成热卤水成矿。 相似文献
92.
A. M. F. Lagmay K. S. Rodolfo F. P. Siringan H. Uy C. Remotigue P. Zamora M. Lapus R. Rodolfo J. Ong 《Bulletin of Volcanology》2007,69(7):797-809
The 1991 Pinatubo eruption left 5–6 km3 of debris on the volcano slopes, much of which has been mobilized into large lahars in the following rainy seasons. Also
during the eruption, collapse, localized in part along preexisting faults, left a caldera 2.5 km in diameter that almost immediately
began to accumulate a 1.6 × 108 m3 lake. By 2001, the water had risen to the fault-controlled Maraunot Notch, the lowest, northwestern portion of the caldera
rim comprising the physiographic sill of the Caldera Lake. That year, a narrow artificial canal dug into an old volcanic breccia
underlying the outlet channel failed to induce a deliberate lake breakout, but discharge from heavy rains in July 2002 rapidly
deepened the notch by 23 m, releasing an estimated 6.5 × 107 m3 of lake water that bulked up into lahars with a volume well in excess of 1.6 × 108 m3. Lakes in other volcanoes have experienced multiple breakouts, providing practical motivation for this study. Fieldwork and
high-resolution digital elevation models reveal andesites and ancient lacustrine deposits, strongly fractured and deformed
along a segment of the Maraunot Fault, a prominent, steeply dipping, left-lateral fault zone that trends N35°–40°W within
and parallel to the notch. Seismicity in 1991 demonstrated that the Maraunot Fault is still active. The fault zone appears
to have previously been the erosional locus for a large channel, filled with avalanche or landslide deposits of an earlier
eruption that were exhumed by the 2002 breakout floods. The deformed lacustrine sediments, with an uncalibrated 14C age of 14,760 ± 40 year BP from a single charcoal sample, attest to the existence of an earlier lake, possibly within the
Tayawan Caldera, rim remnants of which survive as arcuate escarpments. That lake may well have experienced one or more ancient
breakouts as well. The 2002 event greatly reduced the possibility of another such event by scouring away the erodible breccia,
leaving less erodible fractured andesites and lacustrine rocks, and by enlarging the outlet channel and its discharge capacity.
Several lines of evidence indicate, however, that future lahar-generating lake breakouts at the notch may keep populations
of Botolan municipality downstream at risk: (1) a volume of 9.5 × 107 m3 of lake water remains perched 0.8 km above sea level; (2) seismicity in 1991 demonstrated that the Maraunot Fault is still
active and movements of sufficient magnitude could enlarge the outlet and the discharge through it; (3) more likely, however,
with or without earthquake activity, landslides from the steep to overhanging channel walls could block the channel again,
and a major rainstorm could then cause a rise in lake level and sudden breakouts; (4) intrusion of a new dome into the bottom
of the lake, possibly accompanied by phreatic explosions, could expel large volumes of lahar-generating water. 相似文献
93.
94.
Quaternary vertical offset and average slip rate of the Nojima Fault on Awaji Island, Japan 总被引:5,自引:0,他引:5
Abstract Drilling was carried out to penetrate the Nojima Fault where the surface rupture occurred associated with the 1995 Hyogo-ken Nanbu earthquake. Two 500 m boreholes were successfully drilled through the fault zone at a depth of 389.4 m. The drilling data show that the relative uplift of the south-east side of the Nojima Fault (south-west segment) was approximately 230 m. The Nojima branch fault, which branches from the Nojima Fault, is inferred to extend to the Asano Fault. From the structural contour map of basal unconformity of the Kobe Group, the vertical component of displacement of the Nojima branch–Asano Fault is estimated to be 260–310 m. Because the vertical component of displacement on the Nojima Fault of the north-east segment is a total of those of the Nojima Fault of the south-west segment and of the Nojima branch–Asano Fault, it is estimated to total to 490–540 m. From this, the average vertical component of the slip rate on the Nojima Fault is estimated to be 0.4–0.45 m/103 years for the past 1.2 million years. 相似文献
95.
Abstract Crack-filling clays and weathered cracks were observed in the Disaster Prevention Research Institute, Kyoto University (DPRI) 1800 m cores drilled from the Nojima Fault Zone, which was activated during the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake). The crack-filling clays consist mainly of unconsolidated fine-grained materials that fill opening cracks with no shear textures. Most of the cracks observed in the DPRI 1800 m cores are yellow-brown to brown in color due to weathering. Powder X-ray diffraction analyses show that the crack-filling clays are composed mainly of clay minerals and carbonates such as siderite and calcite. Given that the top of the borehole is approximately 45 m above sea level, most of the core is far below the stable groundwater table. Hence, it is suggested that the crack-filling clays and weathered cracks in the cores taken at depths of 1800 m were formed by the flow of surface water down to the deep fractured zone of the Nojima Fault Zone during seismic faulting. 相似文献
96.
The Athens earthquake (7 September 1999): intensity distribution and controlling factors 总被引:1,自引:0,他引:1
The Athens earthquake, Ms=5.9, that occurred on 7th September 1999 with epicenter located at the southern flank of Mount Parnitha (Greece, Attiki) according to instrumental data, is attributed to the reactivation of an ESE–WNW south- dipping fault without surficial expression. The earthquake caused a large number of casualties and extensive damage within an extended area. Damage displayed significant differentiation from place to place, as well as a peculiar geographic distribution. Based on geological, tectonic and morphological characteristics of the affected area and on the elaboration of damage recordings for intensity evaluation, it can be safely suggested that intensity distribution was the result of the combination of a number of parameters both on macro and microscale. On the macroscale, the parameters are the strike of the seismogenic fault, seismic wave directivity effects and to an old NNE–SSW tectonic structure, and they are also responsible for the maximum intensity arrangement in two perpendicular directions ESE–WNW and NNE–SSW. On the microscale, site foundation formations, old tectonic structures buried under recent formations and morphology are the parameters that differentiated intensities within the affected area. 相似文献
97.
Faulting in zones of lithospheric extension: Quantitative analysis of natural and experimental data 总被引:1,自引:0,他引:1
S. I. Sherman 《Pure and Applied Geophysics》1996,146(3-4):421-446
Quantitative relationships between major fault parameters from geological observations and laboratory experiments are compared. Relationships are established between fault length, number, depth of fault penetration, amplitude of displacement and other characteristics. The width of destruction zones is estimated. Spacing between parallel faults of compatible length is evaluated. It is shown that there is a stable correlation between fault length and number, which is independent from the mode of loading the material under destruction. Destruction of the lithosphere is believed to occur according to the laws of deformation of Maxwell elasto-viscous body. 相似文献
98.
青藏块体北缘跨断层测量资料宏观分析 总被引:1,自引:1,他引:1
本文在系统整理青藏块体北缘跨断层测量资料的基础上,进行了形变类型的划分,探讨了不同类型形变所反映的断层运动性能。 相似文献
99.
喜马拉雅构造带于新生代时期经历了两代受力条件截然不同的形变。早期造山挤压形变与造山后的引张形变、青藏高原和高喜马拉雅的大幅度抬升。大致低喜马拉雅范围即青藏高原南缘,现今构造活动与青藏高原和高喜马拉雅块断抬升相辅相成。流行的板块聚合动力学模式,即使早新生代发生过,晚新生代以来已经灯熄。东亚大陆现代形变与地震活动的驱动力不可能源于青藏高原南缘被动挤压,而是取决于与高原隆起相关的深部主动动力学过程 相似文献
100.
河北磁县西部北西西向南山村-岔口活动断裂为北西西向磁县活动断裂西段,全长35km,又可再分为东西两段。全新世时期该断裂有多次活动,活动方式以具左旋性质的正倾滑为主。1830年磁县7.5级地震时,南山村-岔口断裂带出现新的地表破裂,地表垂直位移多处为2~4m,最大约7m。据目前资料,该断裂带最新两次地震事件的时间间隔约为3500a。最近获取的位于磁县最高峰老爷山庙宇碑文资料,补充说明了邻近岔口活动断裂带的古建筑物在1830年地震中的严重破坏。 相似文献