T21A-0161
Geophysical Data of the Pingtung Plain in Southwestern Taiwan
This study uses the gravity data (roughly 50km x 50km) which surveyed in the summer of 2005 to model the density structures beneath the Pingtung Plain. The lowest Bouguer value in Likang is the deepest place of the Pingtung basin. In the modeling, available seismic, drilling and other data are used wherever possible to constrain the geometries and/or densities.We extend the profiles to external sea and expect to discover correlaion between mud diapir and mud volcano in sea and land. Besides, we also reconstruct a new magnetic anomalies map in this area.
T21A-0162
A Physical Modeling Study on Chelungpu Faulting
921 Chi-Chi earthquake has been triggered by Chelungpu faulting in 1999. The fault line extends approximately 100 km from Tongtou to Cholan in a nearly NS direction. Chelungpu fault, also known as Chi-Chi earthquake fault, shows a fracture zone with a width of 1 to 2 km at Fongyuan and turns to EW direction with a 4-km extension to Neiwan with a further NE extension. By referring to the thin-skinned model and the available data, this study carried out physical modeling tests to modify the activity of Chelungpu fault. The initial models of the tests were designed to slide on an inclined plane by considering a low-angle d collement exists in a depth of 3 to 6 km under the Western Foothill region of Taiwan. The modified Chelungpu fault is connected to the d collement at depth in the study. Test results show that rock body overlying the d collement in Western Taiwan accumulate the collision energy from the plate compression in a SE-NW direction, and the rock body deforms and breaks along the existing plane of weakness when its inherent strength is overcome. Surface deformation is intimately related to both the dip angles of the fault plane and d collement. Test results of the model with angles of 8o and 30o for the modified d collement and the fault respectively match most satisfactorily with the available geologic and geophysical data.
T21A-0163
A New Pattern of Tectonic Unit Division in China Continent---The Opinions from the Lithosphere
Based on the differences of geology and geophysics, the different lithospheric types can be classified in China continent. In terms of petrological method, the models of the crust-mantle evolution and orogenic evolution, and the relationship between seismic velocity and rock composition, the petrological structures of lithosphere of eighteen areas in China continent have been set up, and the inhomogeneous characteristics of the crust- mantle composition in China continent have been displayed for the first time. Lithospheres are classified into five types, cratonic, orogenic, rift, marginal-oceanic-crust, and island-arc lithospheres. The lithospheric discontinuity along the western borders of the Sichuan basin, Eerduosi basin, and Yinchuan basin, divides the area into two tectonic units, the east tectonic unit and the west tectonic unit. The east unit has cratonic-type lithospheres, including Eerduosi and Yangtze; Yanshanian orogenic lithospheres, including the Da Hinggan Mountains, Yanshan-Taihangshan, and the middle segment of Nanling. The east unit also has rift-type lithospheres, which include the Song-liao Plain, the north China plain, and Min- yue marginal sea. Additionally, late Cenozoic oceanic crust lithosphere, the Nanhai central sea basin, and island-arc type lithosphere, Taiwan, is present in the east unit. The west unit contains Tarim cratonic-type lithosphere, Paleozoic middle-Asia orogenic lithosphere including Ejinaqi, and Cenozoic orogenic lithospheres, including Tianshan, Altai, Qilianshan, Kunlunshan, and Tethyan-Himalayan. The west unit also contains sub- types of orogenic-type lithosphere, such as Kunlunshan and Qilianshan, which has older material but new structure, Qingtong, which has been thickened after delamination, Gangdisi, which is in the process of delaminating, and the Himalayas, which are currently undergoing thickening. Acknowledgements Our work was supported by the special program of Ministry of Land and Resources of China (No.200010103), National Natural Science Fountain of China(NSFC 402344048, and No.40572063), China Geological Survey Project (1212010561502, 1212010561510, and 1212010561504), and the Key Laboratory of Lithospheric Tectonics and Exploration, China University of Geosciences, Ministry of Education, China (No.2003009, and No.2003010).
T21A-0164
The Relative Crustal Stress Survey in Geothermal Resource Exploration
Uses the natural electromagnetic wave to carry on the relative measurement to the underground crustal stress, is a easy and feasible physical prospecting method; With the method, the relative size of crustal stress value at different depths within the crust can be directly measured, without requiring to drill boreholes into the ground, and without other supplementary means and facilities. Through region survey, not only can determine the position of deep major fault, but also can investigate the underground abnormal terrestrial heat, providing a new geophysical prospecting method for geothermal resource mining.
http://www.mdcb.net
T21A-0165
On the interpretation of geophysical anomalies: evidence from petrophysical database of CCSD
Petrophysical properties of drill cores from main hole of the Chinese Continental Scientific Drilling Program (CCSD) are measured at atmospheric pressure and room temperature in the field laboratory. The correlations among these properties are essential for improving our understanding on how to interpret the conspicuous anomalies recorded in geophysical investigations. Here we present preliminary results from petrophysical properties and their relation to lithology and structure. In this work 500 samples have been measured on their density, ultrasonic velocity, electrical resistivity and magnetic susceptibility. The petrophysical characters of main lithological groups have been established as: high density 3.4$\times$10$^{3}$ kg/m $^{3}$, high velocity7.4$\times$10$^{3}$m/s and high resistivity 15000$\Omega$m rocks (fresh eclogites), low electrical resistivity 150$\Omega$m and high magnetic susceptibility 8.4$\times$10$^{-2}$SI rocks (ultra mafic rocks), low density 2.75$\times$10$^{3}$kg/m$^{3}$ and low velocity 5.6$\times$10$^{3}$m/s rocks (gneisses). Among these groups, the magnetic susceptibility and electrical conductivity will increase with the increasing percentage of metal oxide in the rocks, but the density and velocity decrease with the degree of regression metamorphism. Therefore different lithologies assemblage and proportion induce corresponding characteristic petrophysical values and geophysical response. According to the measured petrophysical database, the cartoon models were given to constrain the anomalies of different physical properties of the rocks. These models illustrate some nature patterns exhibited by the analysed rocks. The possible constituent of the deep crust in this area is inferred from our results. This investigation will make contributions for improving the geological interpretations of the geophysical surveys available in Dabie-Sulu area, eastern China.
T21A-0166
Extracting and Integrating Optimal Landslide Susceptibility Maps
The Generalized Likelihood Uncertainty Estimation (GLUE) was incorporated into a deterministic landslide model (SHALSTAB) to retrieve the best 200 predictions out of the 4000 modeled landslide susceptibility maps. In the GLUE, newly developed success rate acted as criterion to evaluate model efficiency and to search better predictions with optimal parameter combinations, thus, over-estimation in landslide cell prediction and bias due to subjective parameters were eliminated. The 200 best predictions were further used to calculate the cumulative landslide occurrence for each respective cell, thus, an integrated landslide occurrence map (ILOM), which can effectively identify probabilities subject to landsliding, was generated. The Chi-Jia-Wan, a mountainous watershed with high rainfall and steep slope in Taiwan, was assessed successfully that 77 of the 98 actual landslides above 2100 m height fell within areas of $>$50% modeled landslide occurrence. The high- risk area ($>$50% probability) occupied about 16% of the entire watershed implying an absence of over- estimation. Since the ILOM was derived from a combination of maps with multiple parameter sets the ILOM is more informative compared to a single susceptibility map that did not include parameter uncertainties. The extracting and integrating procedure served as a tool for risk assessment, particularly, in those areas with limited budget for watershed preservation and management.
T21A-0167
Inversely Calculated Green's Function and its Applications to the Real Time Simulation of Tsunami Propagation at a Global Scale and to the Construction of a New Type of Tsunami Charts
While the process of tsunami genesis at the epicenter and the process of tsunami inundation over the land are complicated and highly nonlinear, the process of tsunami propagation in the ocean can be satisfactorily modeled by linear shallow water equations. This allows us to use the Green's function and linear superposition principle in preparation for future hazards. A Green function is a fundamental response function in time at a point of interest to a unit forcing at a source point. Being dependent only on the physics and the geometry of the model but not on the actual external forcing, the Green's functions can be pre-calculated. The actual response to a real time arbitrary forcing will be a linear combination of the Green's functions. Due to the mathematical complexity, the Green's functions can only be calculated numerically. Usually one puts a unit forcing at a selected source point, then runs the model forward in getting the responses elsewhere. This usual method is one source point versus many receiving points procedure. It can be repeated for a relatively small number of source points, which are likely chosen within some seismic active zones, but not for all the model grid points, because each source point requires a separate and expensive forward model run whereas a global model with a decent resolution has too many grid points to do so. This presentation will show a new method to calculate the Green's functions. It chooses a receiving point (or called as a point of interest, where, e.g., a populated coastal city is nearby) while regarding all else of the model grids as the potential source points, it then runs the model for the response function at the receiving point to the unit forcings from all the source points. This new method is one receiving point versus many source points procedure. It reverses the positions of the source and receiving points of the usual method; in this sense the Green's functions are inversely calculated. The computational workload for one receiving point with the new method is the same as that for one source point with the usual method. The gain of the new method lies in the fact that we only need to be interested in a relatively small number of coastal points but the protection for these points of interest should be against all possible tsunami sources anywhere in the entire global ocean. This is what we can exactly achieve with the new method. In contrast, the usual method unneededly takes the entire model grid points as the receiving points but the protection it provides is only against a small number of pre-selected source points. This presentation will further demonstrate how to use the Green's functions for running a model in a local domain, or running models in parallel in a series of local domains, but with a global forcing. This will make the real time simulation for tsunami propagation to and through the local domain(s) feasible. It will also introduce a new type of tsunami charts. The commonly seen chart is for travel time of a tsunami starting from an assumed epicenter. Because of the uncertainty in knowing a future epicenter location, charts betted on a few potential sources can never be adequate. With the inversely calculated Green's functions, we can focus on a point of interest, and construct an arrival time chart for all tsunamis from everywhere. Besides, we can also make a gain chart, indicating the maximum amplitude of arrival tsunamis with unit amplitudes at the sources. The assumption for the wave speed is no longer needed and the complex wave reflections and refractions are all contained in the charts.
T21A-0168
Fracture Mechanism of intact Hard Rocks and Earth Science
Laboratory tensile fracture toughness testing on the short rod specimen of Kallax gabbro and Bjorka marble was performed. Servo-controlled loading was employed to obtain the complete load versus displacement curve. Load versus displacement, acoustic emission and microscopic measurements were made. A fluorescent dye was used to trace crack propagation. It was found that the main crack was formed by crack propagation, bifurcation and looping. Although one main crack eventually broke a specimen into two halves, the intact rock around the crack sustained microscopic damage. The maximum acoustic emission rate reached the peak value after the peak load was surpassed. The findings could be applied to the ground seepage studies of oil, gas, ground water, industrial and medicinal waste, pesticide or other chemical solutions. The findings could also be applied to study stress induced rock damage, rock breakage and blasting and, treatment of rock surfaces and materials science. The findings would inspire physicists, philosophers and social activists. The findings were applied to the studies of the natural changes on earth, earthquakes and rockbursts.
http://www.YiXiaoPing.com
T21A-0169
The Comparative Research Between the Earth's Core and Human Heart
The Earth has evolved into an organism from inorganism, and moreover, gestated the most wonderful system of life in the solar system, among which human being is the superlative animal. By contrastive researches, the impregnation of human being has the same process as that of spawns, except the different surrounding. Since the superior animal and the lower animals have the similarity in the process of gestating generation and the Earth gestated the life system, it is conjecture that the organism Earth has the similar structures as that of the superlative animal. The proportion of the human body has the gold symmetry with the heart. Similarly, the north and south pole have the gold symmetry with the Himalayas. We make a contractive research between the Earth's core and the human heart from structure parameters to physics mechanisms. The first step study shows that there is resemblance in electrical character of motion between the Earth's core and Human heart, and the unsymmetrical whirligig of core is the main reason for the origin of geomagnetic field.
T21A-0170
Paleo-incised Valley Sediment in the Southern Changjiang Delta Plain:its Character and Implication to Paleoenvironment
A typical borehole P5 was examined for lithology, dating, spore-pollen and microfossil to reveal the phases of climate-sea level fluctuation and associated sedimentary facies recorded in the paleo-incised valley sediment in the southeast Changjiang delta plain since the last deglaciation. The results show that freshwater marsh prevails in the paleo-incised valley during 15-10 ka BP. A peat layer, 4 m thick, evidence the cooling event of Younger Dryers. Coastal silty sand and silt dominates the strata of paleo-incised valley, suggesting the relative stable sea level during 10-9 ka BP. Clayey silt and silty clay is 11 m thick during 9-8 ka BP, reflecting the rapid deposition in the drowned valley due to the rapid rise of sea level. The deposition surface of the valley approximates to the buried depth of stiff muds in the delta plain at the beginning of the Holocene optimum, indicating the termination of filling in the paleo-incised valley. Keywords paleo-incised valley phases of sea level rise last deglaciation South Changjiang delta plain
http://www.agu.org