DSpace 集合:
https://scholars.lib.ntu.edu.tw/handle/123456789/31343
2024-03-28T17:26:42ZPreliminary Magnetic Mineralogical Studies of the Neopleistocene-Holocene Sediments from Lake Turgoyak
https://scholars.lib.ntu.edu.tw/handle/123456789/641575
標題: Preliminary Magnetic Mineralogical Studies of the Neopleistocene-Holocene Sediments from Lake Turgoyak
作者: Kosareva, L. R.; Nurgalieva, N. G.; Nurgaliev, D. K.; HONGCHUN LI; Krylov, P. S.; Kuzina, D. M.; Antonenko, V. V.
摘要: This article reports on some preliminary findings of a study on the seismoacoustic profiling of the basin of Lake Turgoyak (Southern Urals) and the magnetic properties of its bottom sediments. In the eastern depressions, the lake sediments are up to 8 m thick. The radiocarbon dating of the sediment samples suggests that the lake is at least 25 000 years old. The seismoacoustic data reveal that the lower part of the section, which is composed of the dense Neopleistocene sediments, accumulated when the water level was lower. The Holocene sediments are poorly consolidated silts up to 4 m thick. The magnetic properties of the sediments were found to be indicative of the environmental conditions and fluctuations in the lake level. The high-amplitude variations in the scalar magnetic values of the sediments point to frequent changes in the sedimentation conditions. The sediments with the highest magnetic susceptibility (χ), natural remanent magnetization (NRM), coercive force (Bc), coercivity of remanence (Bcr), saturation magnetization (Ms), and magnetization remanence (Mrs) are likely to have formed during the periods when sedimentary material was transported by ice, often with a significant influence from wind.2023-01-01T00:00:00ZChinese stalagmite δ<sup>18</sup>O records reveal the diverse moisture trajectories during the middle to late last glacial period
https://scholars.lib.ntu.edu.tw/handle/123456789/641569
標題: Chinese stalagmite δ<sup>18</sup>O records reveal the diverse moisture trajectories during the middle to late last glacial period
作者: Yang, Huihui; Chou, Yu Min; Jiang, Xiuyang; Zheng, Wei; He, Yaoqi; Banerjee, Yogaraj; CHUAN-CHOU SHEN; Yu, Tsai Luen; Zhong, Yi; Humbert, Fabien; Liu, Qingsong
摘要: Based on 30 high-resolution U-Th dating controls, we reconstruct stalagmite δ18O records from 45 to 15 thousand years ago (ka B.P., before AD 1950) from the Shizhu Cave, which is located in southwestern China under the influence of both the Indian Summer Monsoon (ISM) and the East Asian Summer Monsoon (EASM). By integrating with the other stalagmite δ18O records in Asia during the middle to late last glacial, our results reveal two main moisture trajectories: one from the Indian Ocean, through the Shizhu Cave towards central China, and the other from the Pacific Ocean to central and northern China. The systematic decrease of the average values of stalagmite δ18O records from oceans to inland China reveals a spatial pattern of water vapour fractionation and moisture trajectory during the middle to late last glacial. In contrast, the variation amplitude, which is defined as the departures apart from the background δ18O records during Heinrich stadials 1 to 4 (HS1–HS4), show an increasing trend from the coastal oceans to mid-latitude inland China, presenting a ‘coastal-inland’ pattern, which can be interpreted by the enhanced East Asian Winter Monsoon (EAWM) and the weakened EASM. More specifically, the enriched stalagmite δ18O records in the EASM region during HS1 to HS4 are caused by the decreased summer rainfall amount or/and the increased proportion of summer moisture resources from the Pacific Ocean. These new observations deepen our understanding of the complicated stalagmite δ18O records in the EASM region.2024-01-01T00:00:00ZLate Holocene paleoclimate reconstruction of northern Taiwan using a multiproxy approach in the Dream Lake sediment core
https://scholars.lib.ntu.edu.tw/handle/123456789/641567
標題: Late Holocene paleoclimate reconstruction of northern Taiwan using a multiproxy approach in the Dream Lake sediment core
作者: Rahman, Abdur; Chang, Wei Cheng; Kashima, Kaoru; Fukumoto, Yu; Steven Huang, Jyh Jaan; LUDVIG LOWEMARK; Wang, Liang Chi; Chang, Yuan Pin
摘要: To understand the role of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM) on the hydroclimate in northern Taiwan, a multiproxy study has been conducted. This study aims to achieve its goal by using micro-XRF data of Ti and sulfur (S), carbon isotopic compositions (δ13C) along with elemental concentrations of carbon (C), nitrogen (N) and S, and diatom analyses in the sediment core extracted from the Dream Lake (DL; 25°10′01.9″ N, 121°33′36.0″ E and elevation = 588 m above sea level), northern Taiwan. The radiocarbon dates revealed that the DL core covered the time interval from 4.5 to 0.4 cal kyr BP. The current records revealed wetter phases during 4.5–3.0 cal kyr BP, 2.0–1.7 cal kyr BP, and 1.0–0.4 cal kyr BP, characterized by the dominance of C3 plants in the DL catchment, increased runoff, and higher lake levels. Drier climates observed in the current study during 3.0–2.0 cal kyr BP and 1.7–1.0 cal kyr BP, marked by a reduction in C3 plants, decreased runoff, and lower lake levels. The northern Taiwan climate during the late Holocene was observed to be regulated by the interplay of EASM and EAWM. The wet climate conditions during 4.5–3.0 were due to the La Niña-like conditions, which led to a strong EASM resulting in high precipitation conditions. The dry climate conditions during 3.0–2.0 cal kyr BP have coincided with El Niño-like conditions during 3.0–2.4 cal kyr BP and a subsequently strong EAWM during 2.4–2.0 cal kyr BP. Both situations led to a reduction in precipitation in the region. Unlike the time frame from 4.5 to 3.0 cal kyr BP, wet climate conditions during 2.0–1.7 and 1.0–0.4 cal kyr BP have coincided with weak EAWM conditions, which led to an increase in precipitation in northern Taiwan. The dry climate noticed between 1.7 and 1.0 cal kyr BP appeared to be the impact of both El Niño-like conditions and strong EAWM.2024-01-01T00:00:00ZDeep learning-based earthquake catalog reveals the seismogenic structures of the 2022 M<inf>W</inf> 6.9 Chihshang earthquake sequence
https://scholars.lib.ntu.edu.tw/handle/123456789/641566
標題: Deep learning-based earthquake catalog reveals the seismogenic structures of the 2022 M<inf>W</inf> 6.9 Chihshang earthquake sequence
作者: Sun, Wei Fang; Pan, Sheng Yan; Huang, Chun Ming; Guan, Zhuo Kang; Yen, I. Chin; Ho, Chun Wei; Chi, Tsung Chih; Ku, Chin Shang; Huang, Bor Shouh; Fu, Ching Chou; HAO KUO-CHEN
摘要: On 18 September 2022, the MW 6.9 Chihshang earthquake struck the south half of the Longitudinal Valley, Taiwan, and caused severe damage. A precise and rapid report for the distribution of aftershock sequence after a devastating earthquake provides key information for deciphering the seismogenic structure in the source region. The utilization of deep-learning methodologies for earthquake event detection offers a significant acceleration in data analysis. In this study, we use SeisBlue, a deep-learning platform/package, to extract the whole earthquake sequence from September to October 2022, including the MW 6.5 Guanshan foreshock, the MW 6.9 mainshock, over 14,000 aftershocks, and 866 foal mechanisms from two sets of broadband networks. After applying hypoDD for earthquakes, the distribution of aftershock sequence clearly depicts not only the Central Range Fault and the Longitudinal Valley Fault but also several local, shallow tectonic structures that have not been observed along the southern Longitudinal Valley.2024-12-01T00:00:00Z