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Currently, two major types of ship-operated underwater instruments are used for heat flow measurements including a Lister-type
heat probe (LTHP) and small temperature loggers (STLs) that are attached to a solid-steel lance or a core barrel. In both
operations, penetration friction heat introduces a transient disturbance to the temperature of the surrounding sediments.
A pragmatic approach is to extrapolate a cylindrical temperature decay function to estimate the equilibrium ambient temperature
(EAT) and equilibrium ambient temperature gradient (EATG) of the sediments from short temperature recordings. The extrapolated
EAT and EATG will greatly affect the estimate of the base of the gas hydrate stability zone (BGHS). In order to achieve a
better extrapolation of EAT, EATG, and 1-s temperature sampling requirements, compact (22.2 cm × 2.2 cm) high-resolution temperature
loggers (CHTLs) have been designed to work with a sediment core barrel. The mechanical and electronic design of the CHTL is
detailed in the text. With a 24-bit, low noise A/D converter embedded in the mix-signal microprocessor, including a highly
stable reference resistor based ratiometric scheme, the CHTL is capable of resolving 0.1 m°C in the range of −1 to 25°C. It
has a memory capacity of 4 Mbyte which can work continually up to 16 days with a 1-s sampling interval. From a data processing
efficiency consideration, field experiments indicate that adopting short support fins to attach the CHTLs to a relatively
small size core barrel is better than using high support fins. A similar approach such as extrapolating the cylindrical temperature
decay function to estimate EAT, EATG can be obtained from regressing a direct calculated temperature gradient of short recorded
data. The resulting EATG accuracy may be significantly improved through the application of the proposed correction formula
and therefore is much better than that which is directly calculated from the extrapolated EATs. 相似文献
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Some features of the arc-continent collision zone in the Ryukyu subduction system, Taiwan Junction area 总被引：1，自引：0，他引：1
Abstract To the northeast of Taiwan, northwestward subduction of the Philippine Sea plate is occurring beneath the Eurasian plate along the Ryukyu Trench. The Ryukyu Trench, which is well defined along the northeastern part of the Ryukyu arc, cannot be easily defined west of 123° east. This is an area where the Gagua Ridge (whose origin is controversial) enters the trench from the south. On the basis of the marine geophysical survey data the following results have been obtained. The structural elements associated with the Ryukyu subduction system deform and partially disappear west of 123° east. Among other things the Ryukyu Trench terminates close to the western slope of the Gagua Ridge. The Gagua Ridge is the result of tectonic heaping and is likely to be an uplifted sliver of oceanic crust. The interaction between the Ryukyu subduction system and the Taiwan collision zone encompasses a wide region from Taiwan to the longitude 124.5° east. The Gagua Ridge is a boundary between the active deformation zone related to the collision in Taiwan and the West Philippine Basin. It is proposed that there is a tectonic zone that can be traced from the Okinawa Trough on the north to the southern termination of the Gagua Ridge on the south. 相似文献
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Transition between the Okinawa trough backarc extension and the Taiwan collision: New insights on the southernmost Ryukyu subduction zone 总被引：4，自引：0，他引：4
Shu-Kun Hsu Jean-Claude Sibuet Serge Monti Chuen-Tien Shyu Char-Shine Liu 《Marine Geophysical Researches》1996,18(2-4):163-187
Located between the Okinawa trough (OT) backarc basin and the collisional zone in Taiwan, the southernmost Ryukyu subduction zone is investigated. This area, including the southwestern portions of the OT and Ryukyu island arc (RA) and located west of 123.5° E, is named the Taiwan-Ryukyu fault zone (TRFZ). West of 123.5° E, the OT displays NNW-SSE structural trends which are different in direction from the ENE-WSW trending pattern of the rest of the OT. Using joint analysis of bathymetric, magnetic, gravity and earthquake data, three major discontinuities, that we interpret as right-lateral strike-slip faults (Faults A, B and C), have been identified. These faults could represent major decouplings in the southern portion of the Ryukyu subduction zone: each decoupling results in a decrease of the horizontal stress on the portion of the RA located on the eastern side of the corresponding fault, which allows the extension of the eastern side of OT to proceed more freely.We demonstrate that the 30° clockwise bending of the southwestern RA and the consecutive faulting in the TRFZ are mainly due to the collision of the Luzon arc with the former RA. After the formation of Fault C, the counterclockwise rotated portion of the ancient RA located west of the Luzon arc was more parallel to the Luzon arc. This configuration should have increased the contact surface and friction between the Luzon arc and the ancient RA, which could have reduced the northward subduction of the Luzon are. Thus, the westward component of the compressive stress from the collision of the Luzon arc should become predominant in the collisional system resulting in the uplift of Taiwan. Presently, because the most active collision of the Luzon arc has migrated to the central Taiwan (at about 23° N; 121.2° E), the southwestern OT has resumed its extension. In addition, the later resistent subduction of the Gagua ridge could have reactivated the pre-existing faults A and B at 1 M.y. ago and present, respectively. From 9 to 4 M.y., a large portion of the Gagua ridge probably collided with the southwestern RA. Because of its large buoyancy, this portion of the ridge resisted to subduct beneath the Okinawa platelet. As a result, we suggest that a large exotic terrane, named the Gagua terrane, was emplaced on the inner side of the present Ryukyu trench. Since that period, the southwestern portion of the Ryukyu trench was segmented into two parallel branches separated by the Gagua ridge: the eastern segment propagated westward along the trench axis while the western segment of the trench retreated along the trench axis. 相似文献
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