Abstract
Magnetic data provides basic information for geological and geophysical interpretation. In this study we compile recently collected (57 cruises survey) and old (published and open access) magnetic data. This compilation includes land, marine and aeromagnetic data acquired in the East Asia region. The newly acquired magnetic data are mainly concentrated mainly in the South China Sea (SCS) (especially in the northern continental shelf), the northwestern part of the West Philippine Basin (WPB), and the East China Sea. The updated magnetic dataset is gridded with a spacing of one arc-minute. The new magnetic map provides new insights into the tectonic setting of East Asia. Analysis of the compiled data reveals several regional anomaly patterns: (1) the NE-SW trending high positive magnetic anomaly zone extending from southwest Taiwan to the area about 114.5°E and 22°N is pronounced; but it is less continuous southwest of the Penghu islands. In addition, the orientation of this high linear magnetic zone changes slightly in 118.5°E, 22.5°N from N60°E - N50°E. (2) Between the Gagua Ridge (GR) and the Luzon-Okinawa Fracture Zone (LOFZ) the marine magnetic stripes of the WPB exhibit a NW-SE orientation. This suggests that the seafloor spreading could be related to the first stage of the WPB east of the LOFZ. (3) The Urdaneta and Amami plateaus are associated with high magnetization zones. These high magnetization zones extend northwestward and are subducting beneath the Ryukyu Trench.
Highlights
Magnetic data generally provide fundamental information on the structural characteristic and the volcanic nature of underlying sources. Hsu et al (1998) compiled shipboard magnetic data offshore Taiwan and aeromagnetic data off western Taiwan and presented a general description of the tectonics around Taiwan
The new magnetic dataset can be used to work on both fundamental and applied researches; especially on the specific questions linked to the structure or tectonics of East Asia
The relative magnetization map shows that the north South China Sea (SCS) margin contains a broad high magnetization zone and high magnetization was located at southwest Taiwan (LMH)
Summary
Magnetic data generally provide fundamental information on the structural characteristic and the volcanic nature of underlying sources. Hsu et al (1998) compiled shipboard magnetic data offshore Taiwan and aeromagnetic data off western Taiwan and presented a general description of the tectonics around Taiwan. Because of some poor data density attributed to the sparseness of existing data sources or the lack of ship tracks in some areas, several magnetic features were still not clear. The coverage of the two global datasets (CCOP 1996; Quesnel et al 2009) are good, some areas still lack ship track lines and the low data density in these areas cannot reflect the local structural characteristics. The newly acquired magnetic data are mainly concentrated in the SCS (especially in the northern continental shelf), the northwestern part of the WPB and the East China Sea. We anticipate that the improved magnetic data will provide new insights into the tectonic features and increase resolution in the local area. Geomagnetic data acquired before year 2010 were reduced to magnetic anomalies by subtracting the total field given by the IGRF11 model (Finlay et al 2010). Due to few permanent observatories inland on Taiwan and the
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