17:15 〜 18:45
[SCG48-P29] Geophysical observations in the Southern Okinawa Trough: Preliminary reports from the Hakuho-maru KH-23-11 cruise
キーワード：沖縄トラフ、背弧海盆、正断層、琉球弧、科学掘削
The Okinawa Trough exhibits a unique tectonic setting, marked by the early stages of back-arc rifting along the continental margin. Studying this region provides insights into the initiation and early phases of back-arc rifting. During the R/V Hakuho-maru KH-23-11 cruise (December 28, 2023 - January 11, 2024), we collected comprehensive geophysical data to examine the variability in tectonic activity across grabens in the southern Okinawa Trough, which is currently in its initial stages of rifting.
Previous studies (e.g., Oshida et al., 1992; Ishihara et al., 2021) have identified two sources explaining trends in regional magnetic anomalies: contemporary igneous activity associated with extension and ancient magnetic anomaly belts established prior to the Pliocene. We verified the consistency of newly acquired data using magnetometer data meticulously compiled, documented, and modeled by these previous studies, enabling the interpretation of data from areas previously not captured.
Detailed studies on gravity anomalies in grabens and surrounding areas are limited due to the lack of information on crustal and sediment thickness, and detailed topographic data. This study utilizes newly acquired gravity and detailed bathymetric data to calculate Bouguer gravity and isostatic anomalies, focusing on variability within the southern Okinawa Trough, using FA2Boug (Fullea et al., 2008). We first compared magnetic calculations with previous studies to confirm their consistency, followed by generating two distinct gravity maps for comprehensive comparison with existing topographic and magnetic maps. This poster will present these preliminary maps and discuss observed variations.
References
Fullea, J., Fernandez, M., Zeyen, H. (2008) FA2BOUG—A FORTRAN 90 code to compute Bouguer gravity anomalies from gridded free-air anomalies: Application to the Atlantic-Mediterranean transition zone. Computers & Geosciences, 34(12), 1665-1681.
Ishihara, T., Uchida, T., CCOP (2021) Magnetic Anomaly Map of East and Southeast Asia. Revised Version (3rd Edition), Digital Geoscience Map P-3 Revised, Geological Survey of Japan.
Oshida, A., Tamaki, K., Kimura, M. (1992) Origin of the magnetic anomalies in the southern Okinawa Trough. Journal of Geomagnetism and Geoelectricity, 44(5), 345-359.
Previous studies (e.g., Oshida et al., 1992; Ishihara et al., 2021) have identified two sources explaining trends in regional magnetic anomalies: contemporary igneous activity associated with extension and ancient magnetic anomaly belts established prior to the Pliocene. We verified the consistency of newly acquired data using magnetometer data meticulously compiled, documented, and modeled by these previous studies, enabling the interpretation of data from areas previously not captured.
Detailed studies on gravity anomalies in grabens and surrounding areas are limited due to the lack of information on crustal and sediment thickness, and detailed topographic data. This study utilizes newly acquired gravity and detailed bathymetric data to calculate Bouguer gravity and isostatic anomalies, focusing on variability within the southern Okinawa Trough, using FA2Boug (Fullea et al., 2008). We first compared magnetic calculations with previous studies to confirm their consistency, followed by generating two distinct gravity maps for comprehensive comparison with existing topographic and magnetic maps. This poster will present these preliminary maps and discuss observed variations.
References
Fullea, J., Fernandez, M., Zeyen, H. (2008) FA2BOUG—A FORTRAN 90 code to compute Bouguer gravity anomalies from gridded free-air anomalies: Application to the Atlantic-Mediterranean transition zone. Computers & Geosciences, 34(12), 1665-1681.
Ishihara, T., Uchida, T., CCOP (2021) Magnetic Anomaly Map of East and Southeast Asia. Revised Version (3rd Edition), Digital Geoscience Map P-3 Revised, Geological Survey of Japan.
Oshida, A., Tamaki, K., Kimura, M. (1992) Origin of the magnetic anomalies in the southern Okinawa Trough. Journal of Geomagnetism and Geoelectricity, 44(5), 345-359.