The Chi-Chi 1999 earthquake: Correlation between the spatio-temporal distribution of aftershocks and viscoelastic stress changes     

Chiou-Fen Shieh  Shyh-Yang Sheu 《Journal of Geodynamics》2008,45(4-5):208-216

The Chi-Chi 1999 (M_L = 7.3) earthquake generated a large number of aftershocks in the vicinity of the rupture plane. The spatial-temporal distribution of these aftershocks was recorded with high precision and thus provided a unique possibility to study whether the correlation between aftershocks and stress changes are primary due to coseismically induced stress changes (static), or whether stress relaxation processes (viscoelastic) in the lower crust contribute significantly to this correlation. From our analysis of a 3D finite element model simulating the viscoelastic stress changes due to the coseismic displacement and tectonic loading we found that the aftershocks are highly correlated with the stress variations (static and viscoelastic) caused by the main shock. Although we found that the correlation between seismicity rate changes and viscoelastic stress fluctuation is slightly better than that of the static stress changes, these differences can only be identified well in the lower crust. As a result, it is reasonable to conclude that static stress changes are the key mechanism for triggering early and shallow aftershocks in the upper crust. It is reasonable to infer that the viscoelastic relaxation in the lower crust does affect the occurrence of early aftershocks in the deep crust, but it does not significantly affect the shallow aftershocks. However, the stress changes induced from the lower crust gradually transfer to the upper crust and may influence the occurrence of aftershocks after a longer time period (>four Maxwell times).  相似文献   

Viscoelastic–afterslip concurrence: a possible mechanism in the early post-seismic deformation of the M_w 7.6, 1999 Chi-Chi (Taiwan) earthquake     

Shyh-Yang Sheu  Chiou-Fen Shieh 《Geophysical Journal International》2004,159(3):1112-1124

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Raman study of shock features in plagioclase feldspar from the Mistastin Lake impact structure,Canada     

Tianqi Xie  Gordon R. Osinski  Sean R. Shieh 《Meteoritics & planetary science》2020,55(7):1471-1490

Plagioclase feldspar is one of the most abundant minerals on the surface of the Earth, the Moon, and Mars, and is also commonly found in meteorites. Studying shock effects in feldspar thus provides us with fundamental information about impact cratering processes on planetary bodies. In this study, plagioclase from monomict and polymict breccias, impact melt rocks, and shock‐metamorphosed target rocks, from throughout the Mistastin Lake impact structure, Canada, was examined using 514 nm laser Raman spectroscopy. As one of the very few impact structures with anorthosite in the target rocks, the Mistastin Lake impact structure provides a unique opportunity to study shocked plagioclase displaying progressive shock metamorphic features. A series of microscopic features was observed within plagioclase, including twins, needle‐like inclusions, planar features, and alteration. The lack of planar deformation features is notable. Raman spectra of these features suggest that this technique is capable of differentiating and classifying shock features in low to moderately shocked rocks. Caution should be exercised, however, as Raman spectra collected from unshocked plagioclase references with known compositions indicate that peak width and peak ratio of the Raman peaks in lower wave number region (<350 cm^?1) and the main signature peaks around 500 cm^?1 vary with chemical composition and crystal orientation. Data collected from diaplectic glass suggest that Raman features are efficient in distinguishing crystalline plagioclase and diaplectic glass. We also observed significant variations in the Raman intensities collected from diaplectic glass, which we ascribe to the localized disorder or inhomogeneity of shock pressure and temperature throughout the target.  相似文献   

The Sr, Nd and O isotopic studies of the 1991–1995 eruption at Unzen, Japan     

Chang-Hwa Chen  Setsuya Nakada  Yuch-Ning Shieh  Donald J. DePaolo 《Journal of Volcanology and Geothermal Research》1999,89(1-4)

The magma generation at Unzen volcano may be considered as the product of crustal material mixed with mantle magma accompanied by fractional crystallization (AFC). The magma in the Unzen volcano is estimated to consist of about 50–80% of residual magma (F) and about 30–70% assimilated crustal material (A) relative to the original magma. Concerning the 1991–1995 eruption, it is estimated that the magma formed as the result of mixing of about 50–60% crustal material and about 55–65% of residual magma. An alternative magma eruption model for the 1991–1995 eruption is proposed here. In the early stage, the isotopic characteristics of 1991 eruption are defined by AFC process in the deeper magma chamber. Later, the magma ascended through the conduit and quiescently stayed for a long time in a shallow reservoir before eruption. The minerals continuously crystallized as phenocrysts especially at the chilled top and outer margin in the shallow chamber. The crystallized phenocryst mush was reworked into the central part of the magma chamber by means of magma convection and rapid magma ascent. Therefore, the reaction between phenocrysts and melt occurs only in internal chemical disequilibrium in the magma chamber. In contrast, the isotopic compositions of the original magma shall be little influenced by the above processes throughout its eruptive history. The 1991–1995 eruptive rocks of the Unzen volcano show their characteristics in Sr and Nd isotopic values independent of their two previous eruptions. However, the isotopic values of early eruptive product could represent the original magma value. This result also supports the previous work of Chen et al. (1993) [Chen, C.H., DePaolo, D.J., Nakada, S., Shieh, Y.N., 1993. Relationship between eruption volume and neodymium isotopic composition at Unzen volcano. Nature 362, 831–834], that suggested the Nd of early or precursory eruptive products could be a qualitative indicator of the maximum size of a continuing or impending eruption.  相似文献   

Raman spectra of stronadelphite Sr5(PO4)3F at high pressures     

Shuangmeng Zhai  Sean R. Shieh  Weihong Xue  Tianqi Xie 《Physics and Chemistry of Minerals》2015,42(7):579-585

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The application of range of variability approach to the assessment of a check dam on riverine habitat alteration   总被引：2，自引：0，他引：2  

Chjeng-Lun Shieh  Yuh-Rong Guh  Shi-Qin Wang 《Environmental Geology》2007,52(3):427-435

This report uses the intermediate disturbance hypothesis to assess the influence of constructing a check dam on river environment. HEC-HMS and HEC-RAS programs were used to generate hydraulic parameters such as flow discharge, water depth, velocity, water surface width and sediment discharge. Indicators of hydrologic alteration (IHA) and indicator of habitat alteration (IHabA) were used to evaluate the flow and habitat conditions before and after check dam construction. The range of variability approach was used to calculate the degree of hydrologic alteration for each IHA, degree of habitat alteration and overall alteration for IHabA. Variability of river habitats before and after check dam construction was contrasted. Alteration became larger the closer to the dam body. An assessment method for check dam construction is offered which does not require ecological investigation data and combines ecology concepts and hydraulics.  相似文献   

Static stress changes as a triggering mechanism of a shallow earthquake: case study of the 1999 Chi-Chi (Taiwan) earthquake   总被引：2，自引：0，他引：2  

Jeng-Cheng WangChiou-Fen Shieh  Tao-Ming Chang 《Physics of the Earth and Planetary Interiors》2003,135(1):17-25

The role of static stress changes in triggering an earthquake has long been debated in the fields of geophysics and fault mechanics. Valuable data sets for the study of static triggering were provided within the 1-year period following the devastating 1999 Chi-Chi (Taiwan) earthquake (M_W=7.6), during which more than 20,000 aftershocks occurred. In this study, stress waves generated by the Chi-Chi earthquake were calculated using a source rupture model in conjunction with a layered elastic model. Static (permanent) stress changes were extracted from the long-period offsets in the stressgrams. Correlations between the calculated stress changes and seismicity were analyzed at different depths and over varying time intervals to ascertain the impact effects of stress changes on triggering aftershocks. Correlations between prior seismicity rates and static stress changes imposed by the Chi-Chi event were low, while correlations between late seismicity rates and static stress changes were much higher. This indicates that static stress changes did affect the occurrence of the Chi-Chi aftershock sequence. The percentage of early aftershocks at shallow depths (0-10 km) in static stress-enhanced areas within 2 weeks of the main shock was high but decreased considerably at greater depths (>10 km) and over longer time periods. It is concluded that static stress changes at depths of 0-10 km played a major role in triggering crustal aftershocks, especially those that occurred within 2 weeks of the main shock. In the deeper crust, static stress changes may have been modified by viscous flow, and at later times, perturbed by earlier, larger aftershocks. Although the correlations between seismicity rate changes and static stress changes are imperfect, a region that was anti-triggered is detected when these two results are compared. Static stress changes are presumably not the only aftershock triggering mechanism, but they definitively play a major role in triggering shallow aftershocks.  相似文献   

An Interactive Sampling Strategy Based on Information Analysis and Ordinary Kriging for Locating Hot Spot Regions     

Shyan-Shu Shieh  Ji-Zheng Chu  Shi-Shang Jang 《Mathematical Geology》2005,37(1):29-48

This study proposes an interactive sampling strategy for locating the hot spot or maximum regions of a concerned attribute in a given area of survey. In the proposed strategy, information analysis is performed based on the ordinary kriging from the existing sample data to suggest a new batch of samples under the criterion of the highest information free energy. The information free energy (F) is a function of information energy (U) and information entropy (S) through F = U - TS, where T is information temperature and is used to coordinate the contribution of U and S to F. Information energy is the value of the concerned attribute, and information entropy is the transformed error variance of kriging and therefore measures the evenness and density of coverage of samples over the area under survey. At early sampling batches, information temperature is high and information entropy dominates the information free energy, and samples are suggested to give an even and dense enough coverage of the whole area under investigation. As samples accumulate, information temperature decreases to enlarge the contribution of information energy, and future samples are taken toward the locations with high attribute values. Two examples demonstrate the efficiency and effectiveness of the proposed sampling strategy in locating the hot spot regions of various fields: (1) a heavy metal contaminated site reproduced by modeling on 55 real field data; (2) a simulated two-dimensional field by the random phase volume (RPV) model. The results show that the proposed strategy, a robust interactive sampling procedure, is able to locate hot spot regions without compromising with the overall profile of an under-survey area.  相似文献   

Reflection of typhoon morakot �� the challenge of compound disaster simulation     

Yu-Shiu Chen  Yu-Shu Kuo  Wen-Chi Lai  Yuan-Jung Tsai  Shin-Ping Lee  Kun-Ting Chen  Chjeng-Lun Shieh 《山地科学学报》2011,8(4):571-581

Climate change has altered locally single-type disasters to large-scale compound disasters because of increasing intensity and frequency of extreme rainfall events. The compound disasters can combine small-scale floods, debris flows, shallow landslides, deep-seated landslides, and landslide lakes into a large-scale single disaster event. Although simulation models and evaluation tools are available for single-type disasters, no single model is well developed for compound disasters due to the difficulty of handling the interrelationship between two successive single-type disasters. This study proposes a structure for linking available single-type simulation models to evaluate compound disasters and provides a useful tool of decision making for warning and planning of disaster reduction.  相似文献   

A numerical simulation of debris flow and its application   总被引：16，自引：0，他引：16  

Cheng-Lun Shieh  Chyan-Deng Jan  Yuan-Fan Tsai 《Natural Hazards》1996,13(1):39-54

Debris flow is the flow of solid-fluid mixture and was treated as the flow of a continuum in routing in this study. A mathematical model was proposed to describe debris flow including deposition process and then solved numerically with suitable boundary conditions. Laboratory experiments were also conducted for comparison and calibration of the numerical results as well as for investigation of debris flow phenomena. The numerical model was also applied to simulate the debris flow caused by heavy rainfall in Tungman village of Hualien County located in the east of Taiwan on 23 June 1990. The simulated bed topographies in alluvial fan were in good agreement with those obtained from laboratory experiments and field observations.  相似文献