High magma storage rates before the 1983 eruption of kilauea, hawaii

After a magnitude 7.2 earthquake in 1975 and before the start of the ongoing eruption in 1983, deformation of Kilauea volcano was the most rapid ever recorded. Three-dimensional numerical modeling shows that this deformation is consistent with the dilation of a dike within Kilauea's rift zones coupled with creep over a narrow area of a low-angle fault beneath the south flank. Magma supply is estimated to be 0.18 cubic kilometers per year, twice that of previous estimates. The 1983 eruption may be a direct consequence of the high rates of magma storage within the rift zone that followed the 1975 earthquake.     

可独立操作半自动轨道式割胶机设计与分析

针对当前我国割胶机成本昂贵、作业难度大等问题,设计了一种可独立操作半自动轨道式割胶机,其机构简单、便于操作.利用Solidworks软件对割胶机进行总体设计,并对导轨装置、行走机构和切割装置进行参数化实体建模,将整机关键零部件导入Solidworks simulation,利用模态频率、静应力、载荷算例进行有限元结构分析,得到前5阶频率振型及应力、应变、位移云图.分析结果表明,振动变形主要发生在抵触杆与橡胶树表皮接触位置,且在小振幅和低阶模态频率(其值达到11.95 Hz)时,导轨装置与行走机构不会产生共振,行走机构没有出现明显的应力、应变集中,但导轨内壁的导向轮容易产生较大的位移变形;L型割胶刀上表面的Mises应力沿切应力方向递增时,割胶刀拉扯阻力将沿相同方向增大,但位移变形量不受影响.本分析为割胶机的设计和改进提供了方法和依据.     

Mantle fault zone beneath Kilauea Volcano,Hawaii

Relocations and focal mechanism analyses of deep earthquakes (>/=13 kilometers) at Kilauea volcano demonstrate that seismicity is focused on an active fault zone at 30-kilometer depth, with seaward slip on a low-angle plane, and other smaller, distinct fault zones. The earthquakes we have analyzed predominantly reflect tectonic faulting in the brittle lithosphere rather than magma movement associated with volcanic activity. The tectonic earthquakes may be induced on preexisting faults by stresses of magmatic origin, although background stresses from volcano loading and lithospheric flexure may also contribute.     

The 2010 Mw 8.8 Maule megathrust earthquake of Central Chile, monitored by GPS

Large earthquakes produce crustal deformation that can be quantified by geodetic measurements, allowing for the determination of the slip distribution on the fault. We used data from Global Positioning System (GPS) networks in Central Chile to infer the static deformation and the kinematics of the 2010 moment magnitude (M(w)) 8.8 Maule megathrust earthquake. From elastic modeling, we found a total rupture length of ~500 kilometers where slip (up to 15 meters) concentrated on two main asperities situated on both sides of the epicenter. We found that rupture reached shallow depths, probably extending up to the trench. Resolvable afterslip occurred in regions of low coseismic slip. The low-frequency hypocenter is relocated 40 kilometers southwest of initial estimates. Rupture propagated bilaterally at about 3.1 kilometers per second, with possible but not fully resolved velocity variations.     

Rapid deformation of the South flank of kilauea volcano, hawaii

The south flank of Kilauea volcano has experienced two large [magnitude (M) 7.2 and M 6.1] earthquakes in the past two decades. Global Positioning System measurements conducted between 1990 and 1993 reveal seaward displacements of Kilauea's central south flank at rates of up to about 10 centimeters per year. In contrast, the northern side of the volcano and the distal ends of the south flank did not displace significantly. The observations can be explained by slip on a low-angle fault beneath the south flank combined with dilation deep within Kilauea's rift system, both at rates of at least 15 centimeters per year.     

Deformation on nearby faults induced by the 1999 Hector Mine earthquake

Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone. We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer-wide zones centered on pre-existing faults. Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake. The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.     

管道在地震断层作用下的位移内力分析

地震断层对管道具有严重影响，它可以使管道产生变形，导致某一中分屈曲，进而影响管道的安全运行。管道穿越地震断层的计算是管道抗震分析的重要内容，而确定管道在这种情况下的位移和内力沿管道的分布，是进一步进行强度和刚度计算的基础。在管道地下移动时位移土抗力模式的基础上，对管道受，为作用在管道上的土抗力可分解为侧向的土压力及沿管轴方向的土壤摩擦力，从而使管道产生侧向移动和轴向移动，以五次Ｂ样条基函数的组合为     

The chi-Chi earthquake sequence: active, out-of-sequence thrust faulting in taiwan

We combined precise focal depths and fault plane solutions of more than 40 events from the 20 September 1999 Chi-Chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central Taiwan is a moderately dipping (20 degrees to 30 degrees ) thrust fault away from the deformation front. A second, subparallel seismic zone lies about 15 kilometers below the main thrust. These seismic zones differ from previous models, indicating that both the basal decollement and relic normal faults are aseismic.     

Deep magma body beneath the summit and rift zones of kilauea volcano, hawaii

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.     

Magma supply rate at kilauea volcano, 1952-1971

The three longest Kilauea eruptions since 1952 produced lava at an overall constant rate of about 9 x 10(6) cubic meters per month (vesicle-free). This is considered to represent the rate of magma supply from a deep source, probably the mantle, because little or no summit deformation indicating high-level storage accompanied any of the three eruptions.     

Kilauea volcano, hawaii: a search for the volcanomagnetic effect

Brief excursions of magnetic field differences between a base station and two satellite station magnetometers show only slight correlation with ground tilt at Kilauea Volcano. This result suggests that only transient, localized stresses occur during prolonged periods of deformation and that the volcano can support no large-scale pattern of shear stresses.     

Linking petrology and seismology at an active volcano

Many active volcanoes exhibit changes in seismicity, ground deformation, and gas emissions, which in some instances arise from magma movement in the crust before eruption. An enduring challenge in volcano monitoring is interpreting signs of unrest in terms of the causal subterranean magmatic processes. We examined over 300 zoned orthopyroxene crystals from the 1980-1986 eruption of Mount St. Helens that record pulsatory intrusions of new magma and volatiles into an existing larger reservoir before the eruption occurred. Diffusion chronometry applied to orthopyroxene crystal rims shows that episodes of magma intrusion correlate temporally with recorded seismicity, providing evidence that some seismic events are related to magma intrusion. These time scales are commensurate with monitoring signals at restless volcanoes, thus improving our ability to forecast volcanic eruptions by using petrology.     

流变效应对面板堆石坝应力变形的影响规律分析

【目的】研究堆石流变效应对面板堆石坝应力变形的影响规律,为预测坝体长期变形规律及应力应变分析提供参考。【方法】结合面板堆石坝工程实际,对堆石料的流变特性、流变计算模型及其有限元计算方法进行了分析与选择,在此基础上,结合国内某高面板堆石坝工程实例,运用三维有限元法,按考虑堆石流变效应和不考虑堆石流变效应2种计算方案,分析了流变效应对大坝应力变形的影响。【结果】流变使坝体及面板的应力变形均呈现增大的趋势,相比较而言,流变对于坝体向上游水平位移的影响最大,对坝体向下游水平位移和坝体竖向位移的影响次之,对面板挠度和面板顺坡向应力的影响则较小;流变对于坝体沉降变形的影响主要发生在堆石填筑后约10个月内;流变引起的附加节点荷载随时间的延长而呈先增大后减小的变化过程,大致在堆石填筑2年以后,流变影响基本消失。【结论】在工程实际中,考虑堆石料的流变效应及其影响是必要的。     

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.     

Co-seismic strike-slip and rupture length produced by the 2001 Ms 8.1 Central Kunlun earthquake

Field investigations show that the surface wave magnitude (Ms) 8.1 Central Kunlun earthquake (Tibetan plateau) of 14 November 2001 produced a nearly 400-kilometer-long surface rupture zone, with as much as 16.3 meters of left-lateral strike-slip along the active Kunlun fault in northern Tibet. The rupture length and maximum displacement are the largest among the co-seismic surface rupture zones reported on so far. The strike-slip motion and the large rupture length generated by the earthquake indicate that the Kunlun fault partitions its deformation into an eastward extrusion of Tibet to accommodate the continuing penetration of the Indian plate into the Eurasian plate.     

New evidence on the state of stress of the san andreas fault system

Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse faults and folds that trend nearly parallel to the San Andreas and that are otherwise unexplainable in terms of strike-slip deformation. Fault-normal crustal compression in central California is proposed to result from the extremely low shear strength of the San Andreas and the slightly convergent relative motion between the Pacific and North American plates. Preliminary in situ stress data from the Cajon Pass scientific drill hole (located 3.6 kilometers northeast of the San Andreas in southern California near San Bernardino, California) are also consistent with a weak fault, as they show no right-lateral shear stress at approximately 2-kilometer depth on planes parallel to the San Andreas fault.     

考虑横向正应力影响的高阶理论及其精化单元法

提出一种新的高阶理论,该理论满足层间位移、应力连续条件,其位移场只有５个未知数,同一阶剪切变形理论中位移函数的未知数一样多,由此建立了三角形精化板单元,该单元满足单元Ｃ＾１类弱连续条件,其收敛性得到保证,且具有列式简单,计算效率和精度高的优点。     

Stress control of deep rift intrusion at Mauna Loa volcano, Hawaii

Mauna Loa volcano, Hawaii, deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano, but it is not known how the spreading is accommodated in the lower part of the volcanic edifice. We present evidence from interferometric synthetic aperture radar data for secular inflation of a dike-like magma body at intermediate depth in the southwest rift zone during 2002 to 2005. Magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes, suggesting that stress transfer plays an important role in controlling subsurface magma accumulation.     

Strain release mechanism of the 1906 san francisco earthquake

Reexamination of geodetic data has shown that aseismic slip occurred on or near the San Andreas fault in the period of about 20 years after 1906. The inferred displacements are comparable to but at greater depths than the sudden slip that occurred at the time of the earthquake. The postseismic slip is constrained only between late 1906 and 1925, and data are insufficient to determine the movements, if any, below about 20 kilometers on the fault. Two independent observations also indicate stubstantial anomalous crustal deformation away from the fault at least 30 years before the earthquake.     

Active normal faulting in the upper Rhine graben and paleoseismic identification of the 1356 Basel earthquake

We have identified an active normal fault in the epicentral area of the Basel (Switzerland) earthquake of 18 October 1356, the largest historical seismic event in central Europe. The event of 1356 and two prehistoric events have been characterized on the fault with geomorphological analysis, geophysical prospecting, and trenching. Carbon-14 dating indicates that the youngest event occurred in the interval 610 to 1475 A.D. and may correspond to the 1356 Basel earthquake. The occurrence of the three earthquakes induced a total of 1.8 meters of vertical displacement in the past 8500 years for a mean uplift rate of 0.21 millimeters per year. These successive ruptures on the normal fault indicate the potential for strong ground movements in the Basel region and should be taken into account to refine the seismic hazard estimates along the Rhine graben.