0不詳3-8 (13)

週二, 09 一月 2007 10:09

General Geochemistry and Geochronology

  • Investigation of the REE tetrad effect and accompanied with unusual geochemical behavior in some highly differentiated granitoids (B.M. Jahn)
  • Studies of organic stable isotope (C, N and S) stratigraphy of Taiwan (Y.G. Chen)
  • Studies of gas geochemistry in various environments of Taiwan (C-H. Chen, T.F. Yang)
  • Precise Ar-Ar dating of the Australasian tektites (C.-H. Lo)
  • Precise Ar-Ar dating of continental basalts from northern China for a better understanding of the causes of the Cretaceous normal superchron (C.-H. Lo)
週二, 09 一月 2007 10:09

Frontier Analytical Geochemistry

  • Development and application of some state-of-the-art analytical techniques, such as high-precision Sr/Ca ratio and attogram-sized 231Pa analysis by TIMS, high-precision U-Th analysis and U-Th-Pa geochronology by quadrupole and sector ICP-MS (single and multi-collectors), to geo- and paleo-climatic sciences (C.C. Shen)
  • The set-up of the mass + elemental analyzer system for 13C and 15N auto-analysis (Y.G. Chen)
  • The set-up of the the TL and OSL dating system in Taiwan (Y.G. Chen)
  • The set-up of the noble gas mass spectrometry and gas geochemistry laboratory (T.F. Yang)
  • The set-up of the step-heating and laser ablation Ar-Ar dating systems (C.H. Lo)
Stalactite from Vietnam provides records of paleo-climatic changes in SE Asia. Field work in Vietnam.
週二, 09 一月 2007 10:09

Big Events in the Geologic Past

  • Super Toba Eruption. Redefined the timing and magnitude of the first Toba Eruption (Sumatra) and suggested that such a super volcanic eruption did not cause any global cooling or glacaition (Lee et al., 2004).
  • Active Volcano in NE Taiwan. Determined the age of the last eruption of Kueishadao, offshore, northeast Taiwan, and therefore pointed out that the volcanic activity of the southern Okinawa Trough is very recent – only 7000 years ago (Chen et al, 2001).
  • Marine Tephrochronolgy. Established for the first time long-term records of volcanic eruptions of the LuzonIslands during the past 2 million years (Wei et al., 1988a, b). Identified the occurrence of volcanic ash in the South China Sea transported from the Youngest Toba eruption 71 thousand years ago (Lee et al., 1999, Song et al., 2000).
  • Australasian Tektites. Lee and Wei (2000) revised the timing, location and magnitude of the big meteoritic impact on the IndochinaPeninsula that yielded the Australasisn strew field 790 thousand years ago. On the other hand, a 40Ar/39Ar dating of the tektites and impact glasses of the Darwin Glass in Australia demonstrated that the materials were formed by a meteorite impact at 807 ± 16 ka (Lo et al., 2002), coinciding with the ages reported for the Australasian tektites found in Southeast Asia and Australia (761-816 ka).
  • Emeishan Basalt Trap. The coincidence in age of the eruption of Emeishan Flood Basalts and the Permian-Triassic boundary suggests that the eruption of Emeishan Trap, rather than the eruption of the Siberian Traps, was responsible for the global d13C excursion and mass extinction (Chung et al., 1998; Lo et al., 2002).

  • Records of climatic changes from ODP and IMAGES cores (left) and the visit of JR to Taiwan (right).
週二, 09 一月 2007 10:09

Paleo-Asian Monsoons and Kuroshio

  • ODP and IMAGES Drilling. Leading proponents (Wei and Chung) from this Department proposed an Ocean Drilling Program to drill the southern Okinawa Trough. ODP Site 1202 penetrated 420 m below seafloor with great success. A history of Kuroshio for the past 60 kyrs has been documented for the first time (Wei et al., 2004, Zhao et al., 2004). More than a dozen long core IMAGES along the western Pacific margin from 6oS to 45oN were also obtained and studied.
  • East Asian Monsoon History. The summer East Asian monsoons were intensified during the interglacial stages during the past 870 thousand years (Wei, et al., 2003). Short-time scale variations of summer and winter monsoons over the past tens of thousand years in Taiwan were reconstructed using pollen records (Liew et al., 2001; Yu et al., 2002).
  • Development of a parallel, multi-domain pseudo-spectral method for simulation of three-dimensional (3-D) seismic wave propagation in generalized inhomogeneous and anisotropic media (S.H. Hung)
  • Theoretical underpinning of the Frechet kernel theory (aka. banana-doughnut theory) as a doctrine of seismic tomography (S.H. Hung)
  • Comprehension of wave-front healing, scattering and other finite-frequency diffraction effects on seismic travel-times by virtue of numerical waveform modeling (S.H. Hung)
  • Advance in the methodology of seismic tomography including multi-resolution banana-doughnut tomography (S.H. Hung) and Leane Tomography–seismic tomography using the Spectral Element method (Y. Gung)
  • Coupling of numerical spectral element and normal-mode methods for efficiently computing accurate synthetic seismograms in a realistic 3-D earth (Y. Gung)
  • Implementation of NACT (nonlinear asymptotic coupling theory) in regional seismic tomography (Y. Gung)
  • Finite element and finite difference modeling of the process of the formation of theTaiwan collision belt (J.C. Hu)
  • Numerical simulation of strain partitioning along Longitudinal Valley Fault in East Taiwan and of stress permutation in brittle tectonics (J.C. Hu)
週二, 09 一月 2007 10:08

Deep Earth

Seismic energy excited by millions of earthquakes denoted by circles is a powerful tool to probe the interior of the earth like X-rays used for CAT scan of a human body.  Lately the traditional thinking of a finite-frequency seismic wave as a light ray such as P, PP and PcP phases (a) has been mended to account for its realistic 3-D banana-shaped sensitivity (b).  This new theory yields significantly-improved tomographic images which reveal a variety of mantle plumes in the mantle.
  • Portrayal of anisotropic fabrics and deformation states in the young Pacific oceanic lithosphere and the Ryukyu subduction-backarc environments as inferred from the observation of seismic polarization anisotropy, specifically shear-wave splitting analysis (S.H. Hung)
  • Mapping lateral variations in the topography of upper mantle seismic discontinuities and the transition zone velocity structure beneath Taiwan and the surrounding region by means of receiver functions and triplication arrivals (S.H. Hung)
  • Determination of robust P and S velocity structures beneath the Iceland hotspot through joint-inversion of multi-frequency seismic travel-time data interpreted by advanced banana-doughnut theory (S.H. Hung)
  • Exploration of the remote heterogeneous “D” layer near the core-mantle boundary as revealed by shear velocity variations varying from a global scale to a highlighted region under the Caribbean and Central America (S.H. Hung)
  • Probing the root of hotspots and a variety of mantle plumes as revealed by a whole-mantle P-velocity anomaly derived from finite-frequency travel-time tomography (S.H. Hung)
  • Illumination of global seismic anisotropic pattern and the thickness of continents constrained by normal-mode waveform tomography (Y. Gung)
  • Construction of global attenuation (Q) structure in the anelastic upper mantle (Y. Gung)
  • Seismic imaging of superplumes from the bottom to the top of the mantle as an implication for heat flux and the thermal evolution within the earth (Y. Gung)
  • Proposition of a mantle plume initiation model for the formation of the Emeishan LIP as designated by geochemical survey (S.L. Chung and C.H. Lo)
  • Characterization of the magmatism and its significance on the tectonic evolution in diverse collisionalenvironments, including the Tibetan plateau, SE Asia, East China, and the Ryukyu-Okinawa subduction-backarc setting (S.L. Chung and C.H. Lo)
    Field work in Tibet.

週二, 09 一月 2007 10:08

Asian Tectonics

  • The Phanerozoic continental growth in central Asia and implications for global continental crust’s composition and evolution (B.M. Jahn)
  • The UHPM and deep continental subduction in eastern China (B.M. Jahn and C.H. Lo)
  • Tibetan-Himalayan tectonomagmatic evolution and environmental impact (S.L. Chung, C.H. Lo and T.F. Yang)
  • The collision-extrusion tectonics and crustal evolution in SE Asia (S.L. Chung and C.H. Lo)
  • The Emeishan LIP formation and its potential effect on the P-Tr boundary events (S.L. Chung and C.H. Lo)
  • Magmatism in the Asian continent and western Pacific marginal seas (C.H. Chen, Y.G. Chen, S.L. Chung, B.M. Jahn, T. K. Liu, C.H. Lo, S.R. Song, and T.F. Yang)
  • Mountain building in Taiwan (W.S. Chen, Y.G. Chen, T. K. Liu, C.H. Lo, S.R. Song, L. S. Teng, C. N. Yang, and T.F. Yang)
    Field work team in Tibet (left), Spectacular structures in Tibet (middle & right)..

週二, 09 一月 2007 10:08

Earthquake Geology of Taiwan

  • Documented the earthquake fault characteristics and related geomorphic features to decipher the mechanism and behavior of the 1999 Chi-chi earthquake (W.S. Chen, Y.G. Chen, J.C. Hu, C.Y. Lu, L. S. Teng, and C. N. Yang)
  • Paleoseismology studies along the Chelungpu fault to reveal the mechanism and to provide slip rates as well as estimated recurrence intervals for this disastrous active fault (W.S. Chen and Y.G. Chen)
  • Using subtle landforms and structure geology to re-evaluate active structures and paleo-seismic history in other neotectonic domains of Taiwan (W.S. Chen, Y.G. Chen and M.L. Hsieh)
  • Using tectono-stratigraphy to reevaluate the earthquake-related sedimentary history of Taipei basin as well as to assess the possible hazards in such a densely populated area (Y.G. Chen and L. S. Teng)
  • Trenching studies along other seismogenic active faults to explore the recent behavior and paleo-seimic records (W.S. Chen).
  • Applying newly developed dating methods (i.e., OSL & TL) to determine the long-term slip rates along the Chelungpu fault, which is consistent with the coseismic slip that occurred in the 1999 Chi-chi earthquake (Y.G. Chen)
  • Numerical modeling of interseismic and coseismic deformation based on GPS data in the Taiwan area (J.C. Hu)
  • Monitoring fault activity and tectonic motions in the Pingtung/Kaohsiung area based on GPS data (J.C. Hu)
    Sedimentary Structure in the late Tertiary foreland basin in Taiwan (published as cover page for Geol. Soc. Amer. Bull.)
  • Relationship between the erosion rate, pre- or post-earthquake, and geohazard of landslide with debris flow (H. Chen, M.L. Hsieh, J.C. Hu and P. M. Liew)
  • Evaluated the geomorphic impact and sea level changes on coastal development (M.L. Hsieh and P. M. Liew)
  • Identification of triggering mechanism of hazardous landslide and debris flow from 1990-2000 inTaiwan (H. Chen)
  • Collection of geomaterial characteristics on various rock types in Taiwan (H. Chen)
  • Finding the relationship between the slope stability and gravel orientation with respect to shape distribution in Taiwan (H. Chen)
  • Established the relationships between strong ground motion peak values and seismic loss during the 1999 Chi-Chi earthquake (Y. M. Wu)
  • Acquisition of GPS data to calculate the strain rate and station velocity in the active deformation zone in Taiwan (J.C. Hu)
  • A new stratigraphic system of the Taipei Basin deposits, including lithostratigraphy and sequence stratigraphy was established (Teng et al., 1999, 2001); Teng (1991, and Teng et al., 2004) proposed also a plate kinematic model for the Tatun volcanism and highlight its potential threat to the Taipei metropolitan area; chemostratigraphy based upon C, N, and S of southwestern coastal plain of Taiwan was established (Ku et al., 2001; Chen et al., 2004; Ku et al., 2004); and, the first optical dating system has been set up for determining ages of sediments by Professor Yue-Gau Chen, a practical application is demonstrated in determining the slip-rate along the Chelungpu fault (Chen et al., 2003)
週二, 09 一月 2007 10:07

Groundwater Resources and Management

  • Conducting groundwater hydrological studies of coastal plains in Taiwan using ratio-isotope and water level change (T. K. Liu).
  • Established the spatial distribution of coseismic groundwater level changes induced by the 1999 Chi-Chi earthquake (Y. P. Chia).
  • Integration of the continuous measurement of flow rate in the borehole to estimate the vertical distribution of hydraulic conductivity of permeable formations (Y. P. Chia)
  • The decline of groundwater level in the TaipeiBasin before the 1970s had caused a serious land subsidence problem (Y. P. Chia)
  • Reassessment of the local hydrogeologic setting rises on the offsite and downward migration of contaminated groundwater and dense non-aqueous phase liquids (Y. P. Chia)
  • Numerical simulation of groundwater level recovery in the confined aquifers during heavy rainfalls along the coastal area of Yunlin (Y. P. Chia)
  • The sustainable development of groundwater resources related to groundwater pollution, excessive pumping, salt water intrusion, and land development (Y. P. Chia)
  • Groundwater hydrology of coastal plains was studied using ratio-isotope and water-level changes (Lee, et al., 2002); geochemical properties of ground water related to endemic diseases were also illuminated (Ku et al., 2001; Oung et al., 2001; Chen and Liu, 2002, 2003; Chang et al., 2003; Ho et al., 2003, Liu and Shih, 2004)