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1.
Based on the theories and methods of cartography on spatial pattern and temporal evolution in Geo-information Tupu (Carto-methodology in Geo-information, CMGI) and the quantitative measurements of pattern and process in landscape ecology, the methodology of landscape information Tupu in studying the swing process of the Yellow River (YR) over the Yellow River Delta (YRD) during 1855―2000 has been demonstrated. The main content includes (1) methodology of landscape information Tupu; (2) evolution process Tupu of YR rump channels; (3) evolution process Tupu of the 7 pieces of subdeltas in YRD during 1855―2000; (4) landscape information Tupu of the modern YRD and the current YRD; (5) landscape information Tupu of YR rump channels on the 7 pieces of subdeltas during 1855―2000; and (6) corridor-matrix landscape information Tupu by YR swings. The methodology of landscape information Tupu here is still primary but we hope that it could provide a new tool for exploring an integrated research on spatiotemporal approaches for landscape "pattern and process".  相似文献   

2.
Based on the theories and methods of cartography on spatial pattern and temporal evolution in Geo-information Tupu (Carto-methodology in Geo-information, CMGI) and the quantitative measurements of pattern and process in landscape ecology, the methodology of landscape information Tupu in studying the swing process of the Yellow River (YR) over the Yellow River Delta (YRD) during 1855―2000 has been demonstrated. The main content includes: (1) methodology of landscape information Tupu; (2) evolution process Tupu of YR rump channels; (3) evolution process Tupu of the 7 pieces of subdeltas in YRD during 1855―2000; (4) landscape information Tupu of the modern YRD and the current YRD; (5) landscape information Tupu of YR rump channels on the 7 pieces of subdeltas during 1855―2000; and (6) corridor-matrix landscape information Tupu by YR swings. The methodology of landscape information Tupu here is still primary but we hope that it could provide a new tool for exploring an integrated research on spatiotemporal approaches for landscape "pattern and process".  相似文献   

3.
It is more and more acknowledged that land-use/cover dynamic change has become a key subject urgently to be dealt with in the study of global environmental change. Supported by the Landsat TM digital images, spatial patterns and temporal variation of land-use change during 1995 –2000 are studied in the paper. According to the land-use dynamic degree model, supported by the 1km GRID data of land-use change and the comprehensive characters of physical, economic and social features, a dynamic regionalization of land-use change is designed to disclose the spatial pattern of land-use change processes. Generally speaking, in the traditional agricultural zones, e.g., Huang-Huai-Hai Plains, Yangtze River Delta and Sichuan Basin, the built-up and residential areas occupy a great proportion of arable land, and in the interlock area of farming and pasturing of northern China and the oases agricultural zones, the reclamation of arable land is conspicuously driven by changes of production conditions, economic benefits and climatic conditions. The implementation of “returning arable land into woodland or grassland” policies has won initial success in some areas, but it is too early to say that the trend of deforestation has been effectively reversed across China. In this paper, the division of dynamic regionalization of land-use change is designed, for the sake of revealing the temporal and spatial features of land-use change and laying the foundation for the study of regional scale land-use changes. Moreover, an integrated study, including studies of spatial pattern and temporal process of land-use change, is carried out in this paper, which is an interesting try on the comparative studies of spatial pattern on change process and the change process of spatial pattern of land-use change.  相似文献   

4.
Using the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: 1 The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; 2 The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; 3 Before the main rupture of the rock sample the obvious “tendency anomaly” and “short-term anomaly” were observed, and some of them could be likely considered as the “impending earthquake” anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically. This subject is supported by the key project during the 8-th “Five Year Plan” from the State Science and Technology Commission of China (85-04-04).  相似文献   

5.
Study on spatial pattern of land-use change in China during 1995—2000   总被引：53，自引：6，他引：53  
Land-use/cover change has become an event being of paramount importance to the study of global environmental change[1,2]. Land-cover change is closely related to the terrestrial surface material cycles and life-support processes[3], i.e., the interaction …  相似文献   

6.
Following a new train of thinking, this paper has explored first the potential information in the ground resistivity data observed by the existing geoelectric observation system, investigated and proposed a new dimensionless geoelectric precursor factor, the degree of ground resistivity anisotropy, S, and studied the characteristics of dynamic evolution pattern of S during the seismogenic process. The results show that, during the seismogenic process, the degree of ground resistivity anisotropy (S) displays a process of 'normal' →'abnormal strengthening (amplitude, range)' →abnormal weakening' → 'earthquake occurrence'→ 'normal'. The earthquake would occur at the time when the S value has entered the late stage of strengthening and turns to weaken and in the gradient belt on the margin of S anomaly region. The dynamic evolution pattern of S reflects the changes of the tectonic stress field during the seismogenic process. Therefore, it would be possible to trace the process of earthquake generation and occurrence from the dynamic evolution pattern of S so as to service earthquake prediction.  相似文献   

7.
Ｓｔｕｄｙｏｎｔｈｅｐａｔｔｅｒｎａｎｄｍｏｄｅｏｆｖｅｒｔｉｃａｌｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｄｕｒｉｎｇｔｈｅｓｅｉｓｍｏｇｅｎｉｃｐｒｏｃｅｓｓｏｆｉｎｔｒａｐｌａｔｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓ杨国华，桂昆长，巩曰沐，杨春花，韩...  相似文献   

8.
The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure,  相似文献   

9.
Using finite element technique of the plane-strain problem in solid-liquid two-phase medium, we studied the characteristics of "field precursors" and "focus precursors" of subsurface fluid and their spatial-temporal evolution in case of dip-slip earthquake. The results show that: ① the change of ground fluid is slow and the anomaly is not prominent in the early period which is of elastic accumulation and non-linear; ②dilatancy emerges and anomaly focus mainly in the source region in the moderate period which is hardening and of local dilatancy. In the period the focus precursors emerge earlier than the field precursors; ③anomalies spread continuously in the source area and new regions with big anomaly emerge out of the source region in the middle-short period which is of large-scale dilatancy.  相似文献   

10.
Particulate fluxes investigated in the central South China Sea (SCS) during 1993―1996 indicate that opal flux can be used to show primary productivity change, which provides a foundation for tracing the evolutionary relationship between the surface productivity and East Asian monsoon in the SCS during the late Quaternary glacial and interglacial periods. Based on the studies of opal % and their mass accumulation rates (MAR) at the six sites recovered from the SCS during the “Resolution” ODP Leg 184 and “Sonne” 95 cruise of the Sino-Germany cooperation, opal % and their MARs increased evidently in the northern sites since 470―900 ka, and they enhanced and reduced, respectively, during the glacial and interglacial periods. Whereas they increased obviously in the southern sites since 420―450 ka, and they augmented and declined, respectively, during the interglacial and glacial periods. The vari- ability in opal % and their MARs in the late Quaternary glacial cyclicity indicate the “seesaw” pattern of surface productivity in the SCS. The winter monsoon intensified during the glacial periods, surface productivity increased and decreased, respectively, in the northern and southern SCS. The summer monsoon strengthened during the interglacial periods, surface productivity increased and decreased, respectively, in the southern and northern SCS. The cross spectral analyses between the opal % in the northern and southern SCS during the Quaternary and global ice volume (δ 18O) and orbital forcing (ETP) indicate that the East Asian winter and summer monsoons could be ascribed to the different drive mechanisms. On the orbital time scale, the global ice volume change could be a dominant factor for the winter monsoon intension and temporal variations. As compared with the winter monsoon, the correlative summer solar radiation with the obliquity and precession in the Northern Hemisphere could be a mostly controlling factor for the summer monsoon intension and temporal variations.  相似文献   

11.
Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the spatial-temporal distribution of “Underground Hot Vortex” (UHV) in China was analyzed in detail. The results show that concerning an “Underground Hot Vortex” cell, its life-span is 3–8 seasons, 1.5 years on average; the mean horizontal scale is 600 km and its characteristic velocity is about 400 km/a; UHV is likely to appear in some areas where the crustal movement is intense and the absolute value of vertical deformation rate is relatively high; its activity could hardly be detected in the area where the crust is stable and the vertical deformation is weak; most of “Underground Hot Vortex Groups” originate from the edge of Indian Plate, then migrate eastwards with a leaping-frog style. 5–10 years are needed for their arrival in the eastern border of China. Their horizontal migrating velocity is 200–500 km/a which is nearly equal to the characteristic velocity of a single UHV. Project sponsored by the National Climbing Project and Key Project of the Chinese Academy of Sciences.  相似文献   

12.
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13.
Variation of snow water resources in northwestern China, 1951–1997   总被引：19，自引：0，他引：19  
Two models are used to simulate the high-altitude permafrost distribution on the Qinghai-Xizang Plateau. The two models are the “altitude model”, a Gaussian distribution function used to describe the latitudinal zonation of permafrost based on the three-dimensional rules of high-altitude permafrost, and the “frost number model”, a dimensionless ratio defined by manipulation of freezing and thawing degree-day sums. The results show that the “altitude model” can simulate the high-altitude permafrost distribution under present climate conditions accurately. Given the essential hypotheses and using the GCM scenarios from HADCM2, the “altitude model” is used for predicting the permafrost distribution change on the Qinghai-Xizang Plateau. The results show that the permafrost on the plateau will not change significantly during 20–50 a, the percentage of the total disappeared area will not be over 19%. However, by the year 2099, if the air temperature increases by an average of 2.91°C on the plateau, the decrease in the area of permafrost will exceed 58%—almost all the permafrost in the southern plateau and in the eastern plateau will disappear. Project “Fundamental Research of Cryosphere” supported by the Chinese Academy of Sciences.  相似文献   

14.
ＴｈｅｐａｔｔｅｒｎｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅｔｅｎｄｅｎｃｙｖａｒｉａｔｉｏｎｓｏｆｅａｒｔｈｒｅｓｉｓｔｉｖｉｔｙａｎｄｉｔｓｒｅｌａｔｉｏｎｔｏｅａｒｔｈｑｕａｋｅｓＨｅ－ＹｕｎＺＨＡＯ（赵和云）（ＥａｒｔｈｑｕａｋｅＲｅｓｅａｒ...  相似文献   

15.
IntroductionShort-to-imminentprecursorsstillarethemainbasisforearthquakepredictioninthepresenttime.Strongquakes,especiallythosewithnoforeshocks,canbeforecastedtosomeextentbasedonabundantshoat-to-imminentprecursorsandcombiningwiththemid-to-longtermvar...  相似文献   

16.
According to the urbanization extent of Beijing area, and with 1980 as a turning point, the duration from 1961 to 2000 is divided into two periods: one is defined as the slow urbanization period from 1961 to 1980, and other one as the fast urbanization period from 1981 to 2000. Based on the 40-year’s precipi-tation data of 14 standard weather stations in Beijing area, the effect of urbanization on precipitation distribution is studied. It is found that there has been a noticeable and systematic change of wi...  相似文献   

17.
This simulation research was conducted in order to develop a large-fire risk assessment system for the contiguous land area of the United States. The modeling system was applied to each of 134 Fire Planning Units (FPUs) to estimate burn probabilities and fire size distributions. To obtain stable estimates of these quantities, fire ignition and growth was simulated for 10,000 to 50,000 “years” of artificial weather. The fire growth simulations, when run repeatedly with different weather and ignition locations, produce burn probabilities and fire behavior distributions at each landscape location (e.g., number of times a “cell” burns at a given intensity divided by the total years). The artificial weather was generated for each land unit using (1) a fire danger rating index known as the Energy Release Component (ERC) which is a proxy for fuel moisture contents, (2) a time-series analysis of ERC to represent daily and seasonal variability, and (3) distributions of wind speed and direction from weather records. Large fire occurrence was stochastically modeled based on historical relationships to ERC. The simulations also required spatial data on fuel structure and topography which were acquired from the LANDFIRE project (). Fire suppression effects were represented by a statistical model that yields a probability of fire containment based on independent predictors of fire growth rates and fuel type. The simulated burn probabilities were comparable to observed patterns across the U.S. over the range of four orders of magnitude, generally falling within a factor of 3 or 4 of historical estimates. Close agreement between simulated and historical fire size distributions suggest that fire sizes are determined by the joint distributions of spatial opportunities for fire growth (dependent on fuels and ignition location) and the temporal opportunities produced by conducive weather sequences. The research demonstrates a practical approach to using fire simulations at very broad scales for purposes of operational planning and perhaps ecological research.  相似文献   

18.
The wave velocity for two types of granitoids was measured using the analytic method of full-wave vibration at high pressure and high temperature. The laws of velocity changes for them differ with the pressure boost and temperature rise, and the velocity change of S-type is more violent than that of I-type. The “softening point” of compressional wave velocity (V μ) is also revealed during the measurement for two types of granitoids imitating the pressure and temperature at a certain depth. But the depth of “softening”, Vp after “softening” and the percentage of Vp’s drop around the “sofrening point” for two types of granitoids are obviously different. The depth of “softening” is 15 km approximately and Vp after “softening” is 5.62 km/s for S-type granitoid. But for I-type granitoid the depth of “softening” is 26 km approximately and Vp after “softening” is 6. 08 km/s. Through careful analysis of rock slices after the experiment, it was found that the “softening” of elastic-wave velocity is caused by the partial melting of granite. Combined with the results of geophysical prospecting, these results suggest that the low-velocity layers developing in the interior of Earth crust are related to thc partial melting of different types of granitoids. The formation of the low-velocity layer in the upper-middle Earth crust is closely related to the development of S-type granitoid, but that in the lower Earth crust is closely related to the development of I-type granitoid.  相似文献   

19.
Conclusion Based on the analysis about the law of deformation rate, the concepts of the deformation rate of precursor, and its stress drop, and the stress drop of instability are discussed. According to the obtained deformationu 0 corresponding to the maximum stress, the unstable pointu 1 and the stable pointu 2 of equilibrium, the complete process of rock failure can be divided into four stages quantitatively, corresponding to “the steady stage I”, “the precursor stage II”, “the unstable stage III” and “the later stage IV” of rock failure respectively, which can be used to simulate the complete course of earthquake. This kind of similarity between the complete process of rock failure and the complete course of earthquake suggests clearly the direction to reveal the law being of universal significance for the simulation of the earthquake in the laboratory experiments. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 517–521, 1991.  相似文献   

20.
Zircon U-Pb results of basalt from the Dashizhai Town in Inner Mongolia, NE China, shows that the basaltic lava was erupted at 439±3 Ma, much older than the “Permian basalts” as previously thought. These rocks show arc-type trace element patterns (i.e., Nb-Ta depletion and light REE and large ion lithophile element enrichment) and unradiogenic Sr and highly radiogenic Nd and Hf isotope compositions. They can be subdivided into two petrogenetic groups: Group 1 basalts have relatively high TiO2, MgO and compatible elements and low Sr and Th, characterized by mid-oceanic ridge basalt (MORB)-type Sr-Nd-Hf isotope compositions (87Sr/86Sr(i)=0.7028−0.7032, εNd(t)=+9.8−+11.2, εHf(t)=+16.1−+18.4). Group 2 has lower TiO2, MgO and compatible elements and higher Sr and Th, and relatively evolved Sr-Nd-Hf isotope compositions (87Sr/86Sr(i)=0.7037−0.7038, εNd(t)=+5.7−+7.3, εHf(t)=+12.6−+13.0). Both groups were interpreted as melts derived from a metasomatized mantle wedge formed during the subduction of Paleo-Asian Ocean. The mantle source for Group 1 was probably a highly isotopically depleted oceanic mantle modified by predominant slab fluids; whereas subducted sediments had an important contribution to the melting source for Group 2. The petrogenesis of the Dashizhai basalts provides clear evidence for early Paleozoic subduction of the Paleo-Asian Ocean, and the highly radiogenic Nd and Hf compositions in these rocks suggest that these lavas and their possible intrusive counterparts were one of the important components for Phanerozoic crustal growth. Our and previous studies on the “Dashizhai Formation” volcanic rocks yield an unrealistic eruption range of 440-270 Ma for different rock types, we thus advise to disassemble the previously defined “Dashizhai Formation” into multiple lithologic units and to reinterpret the spatial and temporal distributions of different volcano-sedimentary associations. Supported by National Basic Research Program of China (Grant No. 2006CB403504)  相似文献   

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