Stress transfer relations among the earthquakes that occurred in Kerman province, southern Iran since 1981   总被引：1，自引：0，他引：1  

Suleyman S. Nalbant  Sandy Steacy  John McCloskey 《Geophysical Journal International》2006,167(1):309-318

We explore the possible stress triggering relationship of the   M ≥ 6.4  earthquakes that occurred in Kerman Province, southern Iran since 1981. We calculated stress changes due to both coseismic sudden movement in the upper crust and the time-dependent viscous relaxation of the lower crust and/or upper mantle following the event. Four events of   M ≥ 6.4  occurred between 1981 and 2005, on and close to the Gowk fault, show a clear Coulomb stress load to failure relationship. The  2003 M = 6.5  Bam earthquake, however, which occurred approximately 95 km SW of the closest Gowk event, shows a very weak stress relation to preceding earthquakes. The coseismic static stress change at the hypocentre of the Bam earthquake is quite small (∼0.006 bars). The time-dependent post-seismic stress change could be 26 times larger or 7 times lower than that of coseismic static stress alone depending on the choice of viscoelastic crustal model and the effective coefficient of friction. Given the uncertainties in the viscoelastic earth models and the effective coefficient of friction, we cannot confidently conclude that the 2003 Bam event was brought closer to failure through coseismic or post-seismic stress loading. Interestingly, the southern Gowk segment with a similar strike to that of the Bam fault, experienced a stress load of up to 8.3 bars between 1981 and 2003, and is yet to have a damaging earthquake.  相似文献   

Physically based modelling of sediment generation and transport under a large rainfall simulator   总被引：1，自引：0，他引：1  

Russell Adams  Sandy Elliott 《水文研究》2006,20(11):2253-2270

A series of large rainfall simulator experiments was conducted in 2002 and 2003 on a small plot located in an experimental catchment in the North Island of New Zealand. These experiments measured both runoff and sediment transport under carefully controlled conditions. A physically based hydrological modelling system (SHETRAN) was then applied to reproduce the observed hydrographs and sedigraphs. SHETRAN uses physically based equations to represent flow and sediment transport, and two erodibility coefficients to model detachment of soil particles by raindrop erosion and overland flow erosion. The rate of raindrop erosion also depended on the amount of bare ground under the simulator; this was estimated before each experiment. These erodibility coefficients were calibrated systematically for summer and winter experiments separately, and lower values were obtained for the summer experiments. Earlier studies using small rainfall simulators in the vicinity of the plot also found the soil to be less erodible in summer and autumn. Limited validation of model parameters was carried out using results from a series of autumn experiments. The modelled suspended sediment load was also sensitive to parameters controlling the generation of runoff from the rainfall simulator plot; therefore, we found that accurate runoff predictions were important for the sediment predictions, especially from the experiments where the pasture cover was good and overland flow erosion was the dominant mechanism. The rainfall simulator experiments showed that the mass of suspended sediment increased post‐grazing, and according to the model this was due to raindrop detachment. The results indicated that grazing cattle or sheep on steeply sloping hill‐country paddocks should be carefully managed, especially in winter, to limit the transport of suspended sediment into watercourses. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The March 25 and 29, 2016 landslide-induced debris flow at Clapar,Banjarnegara, Central Java     

Guruh Samodra  Danang Sri Hadmoko  Ghalih Nur Wicaksono  Indriya Parahita Adi  Maulana Yudinugroho  Sandy Budi Wibowo  Hatma Suryatmojo  Taufik Hery Purwanto  Barandi Sapta Widartono  Franck Lavigne 《Landslides》2018,15(5):985-993

The Clapar landslide induced debris flow consisted of the Clapar landslide occurred on 24 March 2017 and the Clapar debris flow occurred on 29 March 2017. The first investigation of the Clapar landslide induced debris flow was carried out two months after the disaster. It was followed by UAV mapping, extensive interviews, newspaper compilation, visual observation and field measurements, and video analysis in order to understand chronology and triggering mechanism of the landslide induced debris flow in Clapar. The 24 March 2016 landslide occurred after 5 hours of consecutive rainfall (11,2 mm) and was affected by combination of fishponds leak and infiltration of antecedent rain. After five days of the Clapar landslide, landslide partially mobilized to form debris flow where the head scarp of debris flow was located at the foot of the 24 March 2016 landslide. The Clapar debris flow occurred when there was no rainfall. It was not generated by rainstorm or the surface erosion of the river bed, but rather by water infiltration through the crack formed on the toe of the 24 March 2016 landslide. Supply of water to the marine clay deposit might have increased pore water pressure and mobilized the soil layer above. The amount of water accumulated in the temporary pond at the main body of the 24 March 2016 landslide might have also triggered the Clapar debris flow. The area of Clapar landslide still shows the possibility of further retrogression of the landslide body which may induce another debris flow. Understanding precursory factors triggering landslides and debris flows in Banjarnegara based on data from monitoring systems and laboratory experiments is essential to minimize the risk of future landslide.  相似文献   

Approaches to Modelling Long-term Landscape Evolution: Lessons from Ice Sheet Modelling     

Andrew Kerr 《地球表面变化过程与地形》1997,22(3):267-271

Advances in the understanding of physical principles underlying geophysical processes have enabled us to develop complex numerical models of landscape evolution. These advances have shaped recent contributions to the long-running debates within geomorphology concerning the relative value of approaches which emphasize the unchanging (immanent) physical principles underlying geomorphic processes, compared with the historical (configurational) nature of landscapes which rely on circumstantial conditions for their existence. This paper uses examples from glaciology to assess the extent to which the developments in short-term process studies and numerical models assist us in understanding the long-term processes of landscape evolution. The implication is that while both developments stress the immanent nature of geophysics, their limitations highlight the need for a balanced approach incorporating both immanent and configurational approaches. The key is that it is possible to explain and understand long-term processes without necessarily being able to predict them with numerical models. Modelling approaches should stress the contexual nature of the studies by means of a full exploration of possible outcomes of different model components. © 1997 by John Wiley & Sons, Ltd.  相似文献   

Petrogenesis of picrites from the Caribbean Plateau and the North Atlantic magmatic province   总被引：17，自引：0，他引：17  

S. Rvillon  N. T. Arndt  E. Hallot  A. C. Kerr  J. Tarney 《Lithos》1999,49(1-4):1-21

We studied the petrography, mineralogy and geochemistry of picrites from three different regions: the island of Curaçao which forms part of a Cretaceous oceanic plateau; Iceland, an active hot spot on the mid-Atlantic ridge; and the early Tertiary volcanic margin off the coast of Greenland, which formed during the rifting that created the Atlantic ocean. Using the compositions of olivine phenocrysts and relations between MgO and FeO, Al₂O₃ and Ni, we estimated compositions of parental liquids and the proportion of accumulated olivine in each rock. Picrites from Curaçao formed mainly from a liquid with 12 wt.% MgO and they contain up to 55 wt.% excess olivine in the form of phenocrysts. A small proportion of more forsterite-rich olivine grains are xenocrysts from a more magnesian source. Picrites from Iceland formed from a slightly less magnesian liquid but one with also about 12 wt.% MgO and they contain both olivine and plagioclase in the accumulated assemblage. Picrites from the Greenland volcanic margin formed from a liquid that was distinctly more magnesian, with up to 20 wt.% MgO. In some of these rocks the proportion of accumulated olivine was minimal and in these the whole-rock composition is roughly equivalent to the liquid composition. The picrites from the three areas formed under different conditions and through contrasting melting processes. The Curaçao picrites derive from pooled liquids formed through moderate degrees of melting at moderate depths beneath a relatively old and thick oceanic lithosphere. Iceland picrites, on the other hand, formed through advanced fractional melting of mantle that ascended almost to the base of the crust at the mid-ocean spreading center. An unusual combination of relatively high concentrations of incompatible trace elements and high MgO indicates that the Greenland picrites formed by relatively low degrees of melting at greater depths in the mantle.  相似文献   

Influence of water temperature and oxygenation on the aerobic metabolic scope of Atlantic cod (Gadus morhua)     

G. Claireaux  D. M. Webber  J. -P. Lagardre  S. R. Kerr 《Journal of Sea Research》2000,44(3-4)

Environmental influences (temperature and oxygenation) on cod metabolism and their impact on the ecology of this species were investigated. Limiting oxygen concentration curves (O₂ level ranging between 15 and 100% air saturation) were established at 2, 5 and 10°C. The standard metabolic rate (SMR), the maximum metabolic rate and the metabolic scope were then modelled as functions of temperature and/or oxygen saturation. The mean SMR at 2, 5 and 10°C were 19.8±4.9, 30.8±6.1 and 54.3±4.1 mg O₂ h⁻¹ kg⁻¹, respectively. Between 2 and 5°C, the active metabolic rate of cod almost doubled from 65 to 120 mg O₂ h⁻¹ kg⁻¹, to reach 177 mg O₂ h⁻¹ kg⁻¹ at 10°C. In terms of metabolic scope (MS), the temperature rise from 2 to 5°C resulted in a two-fold increase from 45 to 89 mg O₂ h⁻¹ kg⁻¹, with MS reaching 123 mg O₂ h⁻¹ kg⁻¹ at 10°C. Our proposed model describing the impact of temperature and oxygen level provides new insight into the energetic interactions which govern the relationship between Atlantic cod and its environment. We re-examined published experimental and field studies from the angle of the regulation of metabolic power. We suggest that, when faced with heterogeneous or unstable hydrological conditions, cod tend to behaviourally maximise their metabolic scope. Through this adaptive response, fish reduce energy budgeting conflicts and presumably increase the probability of routinely operating away from lethal boundaries.  相似文献   

Simulations of the impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon with modern and mid-Holocene orbital forcings     

Yuefeng Li  Sandy P. Harrison  Ping Zhao  Jianhua Ju 《Global and Planetary Change》2009,66(3-4):235-252

The impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon in modern (0 kyr) and mid-Holocene (6 kyr) climates are investigated by contrasting simulations with and without dynamic vegetation in a coupled ocean-atmosphere model.According to a dynamic index of South Asian summer monsoon, it has been found that the strengths of interannual and interdecadal westerly wind tend not to be affected by the dynamic vegetation over South Asia in the lower troposphere for 0 kyr and 6 kyr. However, based on a dynamic index of western North Pacific (WNP) monsoon, the strengths of tropical westerly wind and south–north cross-equatorial transport are weakened over the tropical western Pacific in the lower troposphere for 0 kyr and 6 kyr. It suggests the impact of dynamic vegetation is more obvious for the WNP monsoon than for the South Asian monsoon. Also, it implies the impact of dynamic vegetation on the interannual and interdecadal circulations is distinctly regional.Singular value decomposition (SVD) analysis shows that the impact of dynamic vegetation can remodel the leading correlation mode (SVD1) between precipitation and surface temperature. All of the interannual and interdecadal precipitation patterns with and without the impact of dynamic vegetation are associated with positive anomalies over India and southeastern China. However, the impact of dynamic vegetation tends to enhance (keep) the positive interannual temperature anomalies of SVD1 over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce the anomalies over the midlatitudinal Eurasia and WNP for 6 kyr. Furthermore, the La Niña-like sea surface temperature (SST) anomalies always dominate the tropics for 0 kyr and 6 kyr. It suggests La Niña-like SST anomalies are the important mechanism to induce the above-mentioned precipitation pattern no matter whether for 0 kyr or for 6 kyr. For the interdecadal surface temperature pattern of SVD1, the impact of dynamic vegetation tends to enhance (reduce) positive anomalies over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce (keep) positive anomalies over the midlatitudinal Eurasia (WNP) for 6 kyr. Also, all of the above implies the impact of dynamic vegetation is a mechanism to induce the long-term change of leading interannual and interdecadal surface temperature pattern over the midlatitudinal Eurasia and/or WNP.  相似文献   

Sensitivity of physical lake processes to climate change within a large Precambrian Shield catchment          下载免费PDF全文

J. Crossman  M. C. Eimers  J. G. Kerr  H. Yao 《水文研究》2016,30(23):4353-4366

Potential future changes in lake physical processes (e.g. stratification and freezing) can be assessed through exploring their sensitivity to climate change, and assessing the current vulnerability of different lake types to plausible changes in meteorological drivers. This study quantifies the impacts of climate change and sensitivity of lake physical processes within a large (5100 km²) Precambrian Shield catchment in south‐central Ontario. Historic regional relationships are established between climate drivers, lake morphology, and lake physical changes through generalized linear modelling (GLM), and are used to quantify likely changes in timing of ice phenology and lake stratification across 72 lakes under a range of future climate models and scenarios. In response to projections of increased temperature (ensemble mean of +3.3 °C), both earlier ice‐off and onset of summer stratification were projected, with later ice‐on and fall turnover compared to the baseline. Process sensitivity to climate change varied by lake type; shallower lakes with a smaller volume (less than 15 m deep and less than 0.05 km³) were more sensitive to processes associated with lake heating (stratification onset and ice‐off), and deeper lakes with a larger surface area (greater than 30 m deep and greater than 1000 ha) were more sensitive to processes associated with lake cooling (fall turnover and ice‐on). These results indicate that whereas small lakes are vulnerable to climate warming because of changes that occur in spring and summer, larger lakes are particularly sensitive during the fall. The findings suggest that lake morphology and associated sensitivity should be considered in the development of sustainable lake management strategies. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Estimating stream solute loads from fixed frequency sampling regimes: the importance of considering multiple solutes and seasonal fluxes in the design of long‐term stream monitoring networks          下载免费PDF全文

Jason G. Kerr  M. Catherine Eimers  Huaxia Yao 《水文研究》2016,30(10):1521-1535

Reduced sampling frequency is known to increase the error associated with estimates of stream solute load. However, the extent to which the magnitude of error differs among commonly measured solutes and across seasons is unclear. In this study, a high sampling frequency data set from two forested streams (one upland‐draining and one wetland‐draining stream) in south‐central Ontario was systematically sub‐sampled to simulate weekly, fortnightly and monthly fixed frequency sampling regimes for 12 stream solutes. We found that solutes which had a higher degree of temporal variation in concentration (i.e. higher %RSD) had poorer precision (C_v) in estimates of annual load relative to solutes with a lower %RSD. In addition, the magnitude and direction of bias varied considerably among solutes and were related to differences in spring concentration‐discharge relationships (m_{[spring Q vs C]}) among the 12 solutes. Solutes which decreased in concentration with increases in spring flow (i.e. m_{[spring Q vs C]} <0) exhibited positive bias in annual load while solutes which increased in concentration with increases in spring flow (i.e. m_{[spring Q vs C]} >0) were negatively biased. In terms of differences between seasonal and annual load errors, precision was generally lower for estimates of seasonal load relative to annual load while bias varied in both magnitude and direction among seasons. When the root mean square error (RMSE) of load estimates was compared to a threshold of acceptable error (<15%), the proportion of solutes attaining acceptable levels of uncertainty ranged from 11/12 for annual load estimates at a weekly sampling frequency to only 4/12 at a monthly frequency when both annual and seasonal loads were considered. Our results demonstrate that commonly measured solutes do not behave uniformly in response to changes in sampling frequency and that estimates of seasonal loads are often less accurate than estimates of annual load. These findings provide important insights into the design of stream monitoring programs and the evaluation of existing long‐term data sets. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

地震来临之前可能会有暗示     

Richard A Kerr  左玉玲 《国际地震动态》2011,(5):16-17

海上的暴风雨会给水手提供合理的警告：气压计度数下降、风向的突然转变以及天空中某些不祥的预兆都预示着暴风雨即将来临。而地震学家却没有这么幸运。数十载的监测未能提供一次即将来临的地震的任何警报信号,因此,多数地震学家都转而研究其他方面的问题。  相似文献