scholarly journals Imaging of the Upper Mantle Beneath Southeast Asia: Constrained by Teleseismic P-Wave Tomography

2020 ◽  
Vol 12 (18) ◽  
pp. 2975
Author(s):  
Huiyan Shi ◽  
Tonglin Li ◽  
Rongzhe Zhang ◽  
Gongcheng Zhang ◽  
Hetian Yang
Keyword(s):  
South China Sea ◽  
Southeast Asia ◽  
Travel Time ◽  
South China ◽  
High Velocity ◽  
Velocity Model ◽  
P Wave ◽  
Deep Part ◽  
Low Velocity ◽  
Velocity Anomalies

It is of great significance to construct a three-dimensional underground velocity model for the study of geodynamics and tectonic evolution. Southeast Asia has attracted much attention due to its complex structural features. In this paper, we collected relative travel time residuals data for 394 stations distributed in Southeast Asia from 2006 to 2019, and 14,011 seismic events were obtained. Then, teleseismic tomography was applied by using relative travel time residuals data to invert the velocity where the fast marching method (FMM) and subspace method were used for every iteration. A novel 3D P-wave velocity model beneath Southeast Asia down to 720 km was obtained using this approach. The tomographic results suggest that the southeastern Tibetan Plateau, the Philippines, Sumatra, and Java, and the deep part of Borneo exhibit high velocity anomalies, while low velocity anomalies were found in the deep part of the South China Sea (SCS) basin and in the shallow part of Borneo and areas near the subduction zone. High velocity anomalies can be correlated to subduction plates and stable land masses, while low velocity anomalies can be correlated to island arcs and upwelling of mantle material caused by subduction plates. We found a southward subducting high velocity body in the Nansha Trough, which was presumed to be a remnant of the subduction of the Dangerous Grounds into Borneo. It is further inferred that the Nansha Trough and the Dangerous Grounds belong to the same tectonic unit. According to the tomographic images, a high velocity body is located in the deep underground of Indochina–Natuna Island–Borneo–Palawan, depth range from 240 km to 660 km. The location of the high velocity body is consistent with the distribution range of the ophiolite belt, so we speculate that the high velocity body is the remnant of thee Proto-South China Sea (PSCS) and Paleo-Tethys. This paper conjectures that the PSCS was the southern branch of Paleo-Tethys and the gateway between Paleo-Tethys and the Paleo-Pacific Ocean. Due to the squeeze of the Australian plate, PSCS closed from west to east in a scissor style, and was eventually extinct under Borneo.

A case study: travel time inversion for P-wave velocity using OBS data of South China Sea

2012 ◽  
Vol 33 (4) ◽  
pp. 389-396 ◽  
Author(s):  
Xiangchun Wang ◽  
Timothy A. Minshull ◽  
Changliang Xia ◽  
Xuewei Liu
Keyword(s):  
South China Sea ◽  
Travel Time ◽  
Wave Velocity ◽  
South China ◽  
P Wave ◽  
Time Inversion ◽  
P Wave Velocity ◽  
Travel Time Inversion ◽  
Obs Data

scholarly journals Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 195
Author(s):  
Yuning Yan ◽  
Jianping Liao ◽  
Junhui Yu ◽  
Changliang Chen ◽  
Guangjian Zhong ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
High Velocity ◽  
Northern South China Sea ◽  
Mud Volcano ◽  
Ocean Bottom ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Mud Volcanism ◽  
Velocity Zone

The Dongsha Island (DS) is located in the mid-northern South China Sea continental margin. The waters around it are underlain by the Chaoshan Depression, a relict Mesozoic sedimentary basin, blanketed by thin Cenozoic sediments but populated with numerous submarine hills with yet less-known nature. A large hill, H110, 300 m high, 10 km wide, appearing in the southeast to the Dongsha Island, is crossed by an ocean bottom seismic and multiple channel seismic surveying lines. The first arrival tomography, using ocean bottom seismic data, showed two obvious phenomena below it: (1) a low-velocity (3.3 to 4 km/s) zone, with size of 20 × 3 km2, centering at ~4.5 km depth and (2) an underlying high-velocity (5.5 to 6.3 km/s) zone of comparable size at ~7 km depth. MCS profiles show much-fragmented Cenozoic sequences, covering a wide chaotic reflection zone within the Mesozoic strata below hill H110. The low-velocity zone corresponds to the chaotic reflection zone and can be interpreted as of highly-fractured and fluid-rich Mesozoic layers. Samples dredged from H110 comprised of illite-bearing authigenic carbonate nodules and rich, deep-water organisms are indicative of hydrocarbon seepage from deep source. Therefore, H110 can be inferred as a mud volcano. The high-velocity zone is interpreted as of magma intrusion, considering that young magmatism was found enhanced over the southern CSD. Furthermore, the origin of H110 can be speculated as thermodynamically driven, i.e., magma from the depths intrudes into the thick Mesozoic strata and promotes petroleum generation, thus, driving mud volcanism. Mud volcanism at H110 and the occurrence of a low-velocity zone below it likely indicates the existence of Mesozoic hydrocarbon reservoir, which is in favor of the petroleum exploration.

scholarly journals Insights from the P Wave Travel Time Tomography in the Upper Mantle Beneath the Central Philippines

2021 ◽  
Vol 13 (13) ◽  
pp. 2449
Author(s):  
Huiyan Shi ◽  
Tonglin Li ◽  
Rui Sun ◽  
Gongbo Zhang ◽  
Rongzhe Zhang ◽  
...  
Keyword(s):  
Travel Time ◽  
Upper Mantle ◽  
High Velocity ◽  
Velocity Structure ◽  
The Philippines ◽  
P Wave ◽  
The South ◽  
Teleseismic Tomography ◽  
The North ◽  
Velocity Anomalies

In this paper, we present a high resolution 3-D tomographic model of the upper mantle obtained from a large number of teleseismic travel time data from the ISC in the central Philippines. There are 2921 teleseismic events and 32,224 useful relative travel time residuals picked to compute the velocity structure in the upper mantle, which was recorded by 87 receivers and satisfied the requirements of teleseismic tomography. Crustal correction was conducted to these data before inversion. The fast-marching method (FMM) and a subspace method were adopted in the forward step and inversion step, respectively. The present tomographic model clearly images steeply subducting high velocity anomalies along the Manila trench in the South China Sea (SCS), which reveals a gradual changing of the subduction angle and a gradual shallowing of the subduction depth from the north to the south. It is speculated that the change in its subduction depth and angle indicates the cessation of the SCS spreading from the north to the south, which also implies that the northern part of the SCS opened earlier than the southern part. Subduction of the Philippine Sea (PS) plate is exhibited between 14° N and 9° N, with its subduction direction changing from westward to eastward near 13° N. In the range of 11° N–9° N, the subduction of the Sulu Sea (SS) lies on the west side of PS plate. It is notable that obvious high velocity anomalies are imaged in the mantle transition zone (MTZ) between 14° N and 9° N, which are identified as the proto-SCS (PSCS) slabs and paleo-Pacific (PP) plate. It extends the location of the paleo-suture of PSCS-PP eastward from Borneo to the Philippines, which should be considered in studying the mechanism of the SCS and the tectonic evolution in SE Asia.

Detection of a Thick and Weak Low‐Velocity Layer atop the Mantle Transition Zone beneath the Northeastern South China Sea from Triplicated P‐Wave Waveform Modeling

2019 ◽  
Vol 109 (4) ◽  
pp. 1181-1193 ◽  
Author(s):  
Guohui Li ◽  
Yunyue Elita Li ◽  
Heng Zhang ◽  
Ling Bai ◽  
Lin Ding ◽  
...  
Keyword(s):  
South China Sea ◽  
Transition Zone ◽  
South China ◽  
P Wave ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
P Wave Velocity ◽  
Low Velocity Layer ◽  
Northeastern South China Sea ◽  
Velocity Layer

Abstract Triplicated P waveforms related to the 410‐km discontinuity from five intermediate‐depth earthquakes in the central Philippines are clearly recorded by the Chinese Digital Seismic Network, but some branches of the S‐wave triplications are obscure. Matching the observed P‐wave triplications with synthetics through a grid‐search technique, we obtain the best‐fit 1D P‐wave velocity model near the 410‐km discontinuity beneath the northeastern South China Sea. In such a model, a low‐velocity layer (LVL) is found to reside atop the mantle transition zone, and it is characterized by a thickness of 92.5±11.5  km and a P‐wave velocity decrement of 1.5%±0.1% compared with the IASP91 model. The relatively thick and weak LVL is possibly a response of a small amount of remnant hydrous partial melts after plume‐like upwelling.

Spatial distribution and origin of the high-velocity lower crust in the northeastern South China Sea

2021 ◽  
pp. 229086
Author(s):  
Jinhui Cheng ◽  
Jiazheng Zhang ◽  
Minghui Zhao ◽  
Feng Du ◽  
Chaoyan Fan ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
South China Sea ◽  
South China ◽  
High Velocity ◽  
Lower Crust ◽  
China Sea ◽  
Northeastern South China Sea

scholarly journals STRATEGI RRC DALAM DINAMIKA KONFLIK DI LAUT CHINA SELATAN

2020 ◽  
Vol 3 (01) ◽  
pp. 113-133
Author(s):  
Ade Priangani ◽  
Jeremy Aldi Rezki Hattu
Keyword(s):  
Political Economy ◽  
South China Sea ◽  
Southeast Asia ◽  
South China ◽  
Major Powers ◽  
Historical Method ◽  
Western Influence ◽  
Difference Of Opinion ◽  
Political Security ◽  
Descriptive Method

South China Sea (SCS) dispute is a matter of seizure or claim of a territory by some countries is indeed a complicated problem. Conflicts involving China with some members of ASEAN have heated up. To improve relations with ASEAN, China through persuasive attitudes and actions. Due to liberalization strategy of China's political economy over SCS especially to ASEAN. The success of ASEAN over the last 50 years has made ASEAN a market share by the major powers that gave birth to a "rivalry". This research uses descriptive method and historical method, where the research is focused on the plan and action of liberalization of China's political economy to face the rivality of the major countries correlation with the dynamics of SCS conflict. The results of this research are: ASEAN succeeded in maintaining peace of political security stability but difference of opinion related issue of sensitive SCS dispute become challenge entering the next 50 years. SCS is actually becoming OBOR's maritime silk line to Southeast Asia. Facing the rivalry of the big countries, China uses its economic card as a control over ASEAN. AIIB as China's bargaining opportunity to ASEAN. So China can easily get rid of western influence and win ASEAN diplomatically.

scholarly journals SPESIES TUMBUHAN ASLI, INTRODUKSI DAN INVASIF DI PULAU BARRANGCADDI SULAWESI SELATAN

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Dody Priosambodo ◽  
Khairul Amri ◽  
Mahatma Lanuru
Keyword(s):  
South China Sea ◽  
Southeast Asia ◽  
Invasive Plants ◽  
South China ◽  
Vascular Plants ◽  
Native Species ◽  
Pacific Coast ◽  
Flowering Plants ◽  
Check List ◽  
Field Guide

Penelitian tentang inventarisasi spesies tumbuhan di pulau Barrangcaddi yang berpenduduk padat telah dilakukan. Tujuan penelitian ini adalah untuk mengetahui jenis-jenis tumbuhan asli, tumbuhan introduksi dan tumbuhan invasif di Pulau Barrangcaddi. Kegiatan sampling dilakukan dengan metode purposive sampling. Data diambil dengan mencatat semua spesies tumbuhan yang ditemukan selama penjelajahan di pulau Barrangcaddi. Seluruh sampel di foto. Sampel tumbuhan yang tidak diketahui namanya, di ambil bagian-bagiannya, kemudian dikoleksi dan diidentifikasi di laboratorium Ilmu Lingkungan dan Kelautan, Departemen Biologi, Fakultas MIPA, Universitas Hasanuddin. Identifikasi sampel menggunakan buku: An Annotated Check-List of The Vascular Plants of The South China Sea and Its Shores oleh Turner et al. (2000) dan Mangrove Guidebook for Southeast Asia oleh Wim Giesen et al. (2007) untuk spesies hutan pantai; Tropical flowering plants: a guide to identification and cultivation oleh Kirsten Albrecht Llamas (2003) untuk spesies tanaman hias dan tanaman budidaya/introduksi serta Nonnative Invasive Plants of Pacific Coast Forest. A Field Guide for Identification oleh Gray et al. (2011) dan Guide to The Naturalized and Invasive Plants of Southeast Asia oleh Arne Witt (2017) untuk spesies tumbuhan invasif. Dari hasil penelitian di pulau Barrangcaddi tercatat sebanyak 142 spesies tumbuhan dari 51 suku. Sebagian besar didominasi oleh tanaman hias dan budidaya (introduksi) dengan 103 spesies dari 42 suku diikuti spesies asli (native species) dengan jumlah 29 spesies dari 19 suku. Spesies invasif tercatat paling sedikit dengan jumlah 10 spesies dari 5 suku. Sebagian besar tutupan vegetasi dari spesies asli telah hilang akibat alih fungsi lahan menjadi permukiman.

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