Spatial and temporal distribution of low frequency volcanic earthquakes in the southern Okinawa Trough back-arc basin

Jing-Yi Lin; Wen-Nan Wu; Chih-Chieh Su; Ching-Hui Tsai; Hsu-Hsiao Sun; Yen-Fu Chen; Shao-Jinn Chin; Yi-Chin Lin

doi:10.3319/tao.2018.12.24.01

Spatial and temporal distribution of low-frequency earthquakes in Japan.

Journal of Physics of the Earth ◽

10.4294/jpe1952.28.361 ◽

1980 ◽

Vol 28 (4) ◽

pp. 361-384 ◽

Cited By ~ 11

Author(s):

Tokuji UTSU

Keyword(s):

Low Frequency ◽

Temporal Distribution ◽

Spatial And Temporal Distribution

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Crustal structure of the southern Okinawa Trough: Symmetrical rifting, submarine volcano, and potential mantle accretion in the continental back‐arc basin

Journal of Geophysical Research Solid Earth ◽

10.1002/2016jb013448 ◽

2017 ◽

Vol 122 (1) ◽

pp. 622-641 ◽

Cited By ~ 29

Author(s):

Ryuta Arai ◽

Shuichi Kodaira ◽

Kaiho Yuka ◽

Tsutomu Takahashi ◽

Seiichi Miura ◽

...

Keyword(s):

Crustal Structure ◽

Okinawa Trough ◽

Submarine Volcano ◽

Southern Okinawa Trough ◽

Back Arc

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3D Seismic Imaging and Geophysical Characteristics of an Embryo Hydrothermal Field in the Southern Okinawa Trough

10.5194/egusphere-egu2020-4063 ◽

2020 ◽

Author(s):

Ho-Han Hsu ◽

Liang-Fu Lin ◽

Tzu-Ting Chen ◽

Char-Shine Liu ◽

Jih-Hsin Chang ◽

...

Keyword(s):

Hydrothermal Fluid ◽

Okinawa Trough ◽

Hydrothermal Field ◽

3D Seismic ◽

Side Scan Sonar ◽

Massive Sulfides ◽

Single Beam ◽

Southern Okinawa Trough ◽

Fault Structures ◽

Back Arc

&#160;&#160;&#160; Multi-scale geophysical survey including pseudo-3D seismic, sub-bottom profiling, side-scan sonar, multi-beam and single-beam bathymetry, heat flow investigations as well as bottom-water, core and dredge sampling works have been conducted in a newly discovered hydrothermal field named as Geolin Mounds at about 1,510 depth in the Okinawa Trough. Ship-mounted bathymetric data cannot detect specific morphological features on the seafloor in this field; however, &#8220;rock grove&#8221; morphological characteristics are observed by using deep-towed side-scan sonar. Moreover, vigorous flare features in water column are detected by multi-beam and single-beam echo sounder, and widely distributed high heat flow anomalies (> 10,000 mW/m2) also exist in the survey area. Due to strong Kuroshio Current during our multi-channel seismic survey, 5-40&#176;streamer feathering effect occurred. To take advantage of swath distributed seismic reflection points caused by streamer feathering, we developed a pseudo-3D technique and produced a 3D seismic cube from this uneven seismic dataset. The 3D seismic imaging and sub-bottom profiling results indicate widely-distributed anomalies such as blanking zone and high-amplitude reflectors around the Geolin Mounds hydrothermal field and could link the specific features above seafloor. The 3D seismic cube also provides better estimation of the areas of blanking zone on selected time slice and better characterizes fault structures in the hydrothermal field. The geochemical analysis results present high Ag, Au, As, Bi, Cd, Cu, Fe, Pb, Sb, and Zn concentrations have been found in our coring and dredging samples. Relatively high concentration of methane, rare earth elements and 3He/4He ratio in near bottom seawater samples are also shown. Based on the geophysical and geochemical works, we propose that the Geolin Mounds hydrothermal field is without underlying submarine volcanos and hydrothermal fluid migration could be related to fault development. This hydrothermal field is in its embryo stage of evolution and constantly supported by active hydrothermal circulation. As a consequence, seafloor massive sulfides deposits and related geomorphological features can keep developing with hydrothermal fluid circulation along migration conduits. The fault structures and volcanic activities due to back-arc spreading process in the Southern Okinawa Trough should dominated creatures of those fluid migrating conduits.&#160; We suggest that the Geolin Mounds hydrothermal field could sustainably grow and have high potential of massive sulfides resources in the Southern Okinawa Trough. Furthermore, this hydrothermal field can serve as a good observatory for get better understanding of seafloor edifice development and ore mineralization associated with hydrothermal circulation activities in a back-arc spreading tectonics.

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Characteristics of seismicity in the southern Okinawa Trough and their relation to back-arc rifting processes

Earth Planets and Space ◽

10.1186/s40623-021-01491-4 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Ryuta Arai

Keyword(s):

Seismic Reflection ◽

Okinawa Trough ◽

Statistical Characteristics ◽

Ryukyu Islands ◽

Seismic Reflection Data ◽

Seismicity Rate ◽

Southern Okinawa Trough ◽

The Ryukyu Islands ◽

Stress Changes ◽

Back Arc

AbstractThe southern part of the Okinawa Trough forms a narrow back-arc rift basin where evidence for submarine volcanoes and active hydrothermal venting is observed. The region is also known to cause large crustal earthquakes frequently which often accompany a rapid increase in seismicity rate. Although such swarm-like activities are common in active volcanic regions and are considered to be primarily induced by crustal fluid flows, potential interactions between tectonic, magmatic and hydrologic processes have been poorly examined in the southern Okinawa Trough despite these processes happening in the proximity. Here, I report the spatial and statistical characteristics of seismic activity in the southern Okinawa Trough and discuss their relation to other rifting-related phenomena. Most of the earthquakes with magnitude greater than 5 are localized around the rift axes (the Yaeyama Rift and the Yonaguni Rift) where seismic reflection data indicated the presence of solidified magmatic intrusions into the shallow sedimentary layers. I found the areas around the rift axes show low b values of < 0.8 and suggest that stress changes directly induced by dike intrusions beneath the rift axes control the occurrence of swarm activities. On the contrary, regions with high b values (> 1.2) are found around the Ishigaki Knoll and the Hatoma Knoll. These two areas are located between the rift axes and the Ryukyu Islands and correspond to potential submarine volcanoes proposed by seafloor bathymetry and seismic reflection images. This result may constrain the location of the volcanic front in the region.

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Spatial and Temporal Distribution of the Neutral Polymorphisms in the Last ZFX Intron: Analysis of the Haplotype Structure and Genealogy

Genetics ◽

10.1093/genetics/152.3.1091 ◽

1999 ◽

Vol 152 (3) ◽

pp. 1091-1101 ◽

Cited By ~ 7

Author(s):

Jadwiga Jaruzelska ◽

Ewa Zietkiewicz ◽

Mark Batzer ◽

David E C Cole ◽

Jean-Paul Moisan ◽

...

Keyword(s):

Low Frequency ◽

Temporal Distribution ◽

Recent Common Ancestor ◽

Human Populations ◽

Ancestral State ◽

Spatial And Temporal Distribution ◽

Nucleotide Polymorphisms ◽

African Origin ◽

Most Recent Common Ancestor ◽

The Common

Abstract With 10 segregating sites (simple nucleotide polymorphisms) in the last intron (1089 bp) of the ZFX gene we have observed 11 haplotypes in 336 chromosomes representing a worldwide array of 15 human populations. Two haplotypes representing 77% of all chromosomes were distributed almost evenly among four continents. Five of the remaining haplotypes were detected in Africa and 4 others were restricted to Eurasia and the Americas. Using the information about the ancestral state of the segregating positions (inferred from human-great ape comparisons), we applied coalescent analysis to estimate the age of the polymorphisms and the resulting haplotypes. The oldest haplotype, with the ancestral alleles at all the sites, was observed at low frequency only in two groups of African origin. Its estimated age of 740 to 1100 kyr corresponded to the time to the most recent common ancestor. The two most frequent worldwide distributed haplotypes were estimated at 550 to 840 and 260 to 400 kyr, respectively, while the age of the continentally restricted polymorphisms was 120 to 180 kyr and smaller. Comparison of spatial and temporal distribution of the ZFX haplotypes suggests that modern humans diverged from the common ancestral stock in the Middle Paleolithic era. Subsequent range expansion prevented substantial gene flow among continents, separating African groups from populations that colonized Eurasia and the New World.

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