Liu Char-Shine

No Thumbnail Available
Last Name
Liu
First Name
Char-Shine
ORCID

Filters

2004 - 2009 2 2010 - 2012 1
3
3
Reset filters

Settings

Search Results

Now showing 1 - 3 of 3
  • Article
    Estimate of the bottom compressional wave speed profile in the northeastern South China Sea using "Sources of Opportunity"
    (IEEE, 2004-10) Lin, Ying-Tsong ; Lynch, James F. ; Chotiros, Nicholas P. ; Chen, Chi-Fang ; Newhall, Arthur E. ; Turgut, Altan ; Schock, Steven G. ; Chiu, Ching-Sang ; Bartek, Louis R. ; Liu, Char-Shine
    The inversion of a broad-band "source of opportunity" signal for bottom geoacoustic parameters in the northeastern South China Sea (SCS) is presented, which supplements the towed source and chirp sonar bottom inversions that were performed as part of the Asian Seas International Acoustics Experiment (ASIAEX). This source of opportunity was most likely a "dynamite fishing" signal, which has sufficient low-frequency content (5-500 Hz) to make it complimentary to the somewhat higher frequency J-15-3 towed source (50-260 Hz) signals and the much higher frequency (1-10 kHz) chirp signals. This low frequency content will penetrate deeper into the bottom, thus extending the other inverse results. Localization of the source is discussed, using both a horizontal array for azimuthal steering and the "water wave" part of the pulse arrival for distance estimation. A linear broad-band inverse is performed, and three new variants of the broad-band inverse, based on: 1) the Airy phase; 2) the cutoff frequency; and 3) a range-dependent medium are presented. A multilayer model of the bottom compressional wave speed is obtained, and error estimates for this model are shown, both for the range-independent approximation to the waveguide and for the range-dependent waveguide. Directions for future research are discussed.
  • Article
    Two-station measurement of Rayleigh-wave phase velocities for the Huatung basin, the westernmost Philippine Sea, with OBS : implications for regional tectonics
    (John Wiley & Sons, 2009-10-28) Kuo, Ban-Yuan ; Chi, Wu-Cheng ; Lin, Ching-Ren ; Chang, Emmy Tsui-Yu ; Collins, John A. ; Liu, Char-Shine
    A broad-band ocean-bottom seismometer (OBS) deployed ~180 km east of Taiwan provides a first glimpse into the upper mantle beneath the westernmost section of the Philippine Sea or the Huatung basin (HB). We measured interstation phase velocities of Rayleigh waves between the OBS and stations on the eastern coast of Taiwan. The phase velocities show smooth variations from 3.8 to 3.9 km s−1 for periods of 25–40 s. In this short period range, phase velocities are comparable to those characterizing the 15–30 Ma Parece-Vela basin of the Philippine Sea. Modelling of the finite-frequency effect proves the validity of the measurement for the average HB. The shear-wave velocity models inverted from the 25 to 40 s dispersion show a velocity at lithospheric depths about 0.1 km s−1 lower than that of the west Philippine Sea, which agrees with the age effect derived from the Pacific pure-path model. Inversions incorporating the less reliable data above 40 s yield a shear velocity <4.0 km s−1 below 150 km, an unrealistic value even for a hotspot plume environment. The seismological evidence, together with the correlation in seafloor depth, suggests that the HB and the Parece-Vela basin may have a similar age. This is at odds with the previous geochronological study suggesting an early-Cretaceous age for the HB. Thermal rejuvenation of the lithosphere was examined as a potential solution to reconciling the two age models.
  • Article
    Seasonal changes in gaseous elemental mercury in relation to monsoon cycling over the northern South China Sea
    (Copernicus Publications on behalf of the European Geosciences Union, 2012-08-16) Tseng, Chun-Mao ; Liu, Char-Shine ; Lamborg, Carl H.
    The distribution of gaseous elemental mercury (GEM) was determined in the surface atmosphere of the northern South China Sea (SCS) during 12 SEATS cruises between May 2003 and December 2005. The sampling and analysis of GEM were performed on board ship by using an on-line mercury analyzer (GEMA). Distinct annual patterns were observed for the GEM with a winter maximum of 5.7 ± 0.2 ng m−3 (n = 3) and minimum in summer (2.8 ± 0.2; n = 3), with concentrations elevated 2–3 times global background values. Source tracking through backward air trajectory analysis demonstrated that during the northeast monsoon (winter), air masses came from Eurasia, bringing continental- and industrial-derived GEM to the SCS. In contrast, during summer southwest monsoon and inter-monsoon, air masses were from the Indochina Peninsula and Indian Ocean and west Pacific Ocean. This demonstrates the impact that long-range transport, as controlled by seasonal monsoons, has on the Hg atmospheric distribution and cycling in the SCS.