GPS Medium-Range Kinematic Positioning for the Seafloor Geodesy of Eastern Taiwan

To realize the plate motion of the Philippine Sea Plate (PSP) and the characteristics of crustal deformation in the plate boundary zone between the PSP and Eurasia Plate, three seafloor geodetic arrays using a combination of GPS kinematic positioning and acoustic ranging techniques have been established off eastern Taiwan since 2008. Each array is composed of three transponders deployed on the ocean bottom in a triangular shape and has been observed at least two times since 2009. The GPS kinematic positioning in the relative distance ranging from 80 to 120 km off the eastern coast of Taiwan plays a main role in the whole seafloor geodetic deformation system. Seven stations from Taiwan Continuous GPS Array are taken as reference sites and three or four rover GPS units are set up on the vessel or buoy. Both on-land reference and onboard rover receivers record data in sampling rates of 1 and 5 Hz to determine the instantaneous positions of transducer onboard which transmits and receives the acoustic signal to and from seafloor transponders and the attitude of vessel or buoy in kinematic mode. We compare the results of medium-range kinematic positioning between the on-land reference stations and rovers onboard by the GrafNav and Bernese V5.0 software, respectively. In addition, we determine the attitude at all times by way of computing the inter-distance of rover receivers onboard. Hence there are two positioning results can be estimated which are direct (by short relative distances from onboard) and indirect (by medium-range kinematic mode for each GPS unit from on-land continuous stations) methods, and the difference reveals in decimeter level

Interseismic Deformation and Earthquake Hazard along the Southernmost Longitudinal Valley Fault, Eastern Taiwan

About half of the 8  cm/yr of oblique convergence across the active convergent plate boundaries of Taiwan occurs in eastern Taiwan, across the Longitudinal Valley. Significant shortening and left‐lateral slip occurs across the Longitudinal Valley fault there, both as shallow fault creep and as seismogenic fault slip. The southernmost Longitudinal Valley fault comprises an eastern Peinan strand and a western Luyeh strand. We derive an interseismic block model for these two strands using data from a small‐aperture Global Positioning System (GPS) campaign and leveling. The model provides estimates of fault slip rates and quantifies slip partitioning between the two strands. A 45  mm/yr dip‐slip rate on the northern Peinan strand diminishes southward, whereas the left‐lateral component increases. In contrast, nearly pure dip‐slip motion of about 20  mm/yr on the southern Luyeh strand diminishes northward to about 8  mm/yr and picks up a component of left‐lateral motion of about 15  mm/yr before it dies out altogether at its northern terminus. The Luyeh and the northern Peinan strands record near‐surface creep, but the southern Peinan strand appears locked. The potential earthquake magnitude for the two strands may be as high as M_w 6.5. We anticipate seismic rupture mainly on the locked portion of the Peinan strand

Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills

The Taiwanese range has resulted from the collision between the Luzon volcanic arc and the Chinese continental margin, which started about 6.5 Myr ago in the north, and has since propagated southward. The building of the range has been recorded in the spatiotemporal evolution of the foreland basin. We analyze this sedimentary record to place some constraints on the kinematics of crustal deformation. The flexure of the foreland under the load of the growing wedge started with a 1.5 Myr long phase of rapid subsidence and sedimentation, which has migrated southward over the last 3.5 Myr at a rate of 31 +10/−5 mm/yr, reflecting the structural evolution of the range and the growth of the topography during the oblique collision. Isopachs from the Toukoshan (~0 to 1.1 Ma) and Cholan (~1.1 to 3.3 Ma) formations, as well as the sedimentation rates retrieved from a well on the Pakuashan anticline, indicate that the foreland basement has been moving toward the center of mass of the orogen by ~45–50 mm/yr during the development of the basin. From there, we estimate the long-term shortening rate across the range to 39.5–44.5 mm/yr. By considering available data on the thrust faults of the foothills of central Taiwan, we show that most (if not all) the shortening across the range is accommodated by the most frontal structures, with little if any internal shortening within the wedge. The range growth appears therefore to have been essentially sustained by underplating rather than by frontal accretion. In addition, only the upper ~7 to 9 km of the underthrusted crust participates to the growth of the orogen. This requires that a significant amount of the Chinese passive margin crust is subducted beneath the Philippine Sea plate

台2線 68K 八斗子滾石災害致災成因初探

基隆市北寧路於2013 年8 月31 日下午發生高強度降雨事件 (最高達94.5 mm/hr)，並導致台2 線68K+000 處於當日16 時19 分左右發生落石擊毀小客車之意外。本次落石災害之發生區屬於大寮層中段塊狀砂岩，且為逆向坡之型態，現地調查結果顯示本區域具有兩組傾角近乎垂直之節理面，一組走向約略平行於海岸線，另一組走向則約略垂直於海岸線。致災成因可能與長期雨水入滲及風化作用有關，節理裂隙除因風化作用逐漸加大外，節理面上之含鐵質結核亦可能於風化後體積增加，進而加速節理開裂速度。本次落石災害之運動歷程大致可分為傾倒、滾動、墜落、彈跳、滾動等數段歷程，落石運動過程耗時約23 秒，移動路徑上之植被與風化土壤層可能為遲滯落石運動之主因。本文將說明此次災害之地質調查成果，並探討可能之破壞機制，以供未來類似災害之防治對策參考。Several rockfalls caused damages on Highway No.2 during an intensive rainfall on August 31, 2013, in Keelung. One of the rockfalls hit a car and the event was captured by a camera. This study analyzes the mechanism of the rockfall based on the video and field investigation. Two major joints which led to the hazard, one was parallel to the coast and the other was perpendicular to the coast. Both of them were almost vertical and cut the rock into several blocks. Weathering processes may have lead to the extension of joints during the heavy rainfall; the infiltration and the surface runoff took the weathered material away, making the rock unable and ultimately leading to the rockfall. The process of this hazard can be divided into topple, roll, fall, bounce and roll. The rockfall took about 23 seconds in total. This paper focuses on the results of field investigation and the mechanism of the rockfall is also discussed

Coseismic Surface GPS Displacement and Ground Shaking Associated with the 2006 Pingtung Earthquake Doublet, Offshore Southern Taiwan

[[sponsorship]]地球科學研究所[[note]]已出版;[SCI];有審查制度;具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=1017-0839&DestApp=JCR&RQ=IF_CAT_BOXPLO

BIOGRAPHY An Instantaneous Ambiguity Resolution Procedure Suitable for Medium-Scale GPS Reference Station Networks

Taiwan. He is currently a Ph.D. student in the Schoo

Strain Accumulation in Southwestern Taiwan

The 1990-1997 annually surveyed GPS data form 36 stations and continuous data form 3 permanent stations in southwestern Taiwan are utilized to study the spatial and temporal variations of crustal strain in the area. Moderate to remarkable contraction rates of 0.48-2.01 m strain/yr in 91 degree- 135 degree are observed in the vicinity of the Chukou fault (CKF). The contraction rates decrease toward either the east or the west. Along the surface trace of the CKF, the strain rates of the northern segment are approximately at the same level, while that for the central and southern segments clearly increase toward the south. The temporal variations of crustal strain near the CKF are quite uniform during the period from 1990 to 1997. Analyzing the repeated GPS data of a dense profile across the central segment of the CKF from 1993 to 1997, it is found that the E-W shortening is distributed at several places and is not solely due to slip along the CKF. The east velocity components relative to Penghu increase dramatically form 2.6 mm/yr near the western coast to 39.9 mm/yr in the foothill region to the east of the CKF. These results indicate that crustal strain is accumulating rapidly and that there is a very high possibility of a forthcoming major earthquake in the Chianan area. The extremely high strain rates in the southern segment of the CKF may be caused by the aseismic slip on the fault as the seismic activity here is insignificant

Phasor Representation for Narrowband Active Noise Control Systems

The phasor representation is introduced to identify the characteristic of the active noise control (ANC) systems. The conventional representation, transfer function, cannot explain the fact that the performance will be degraded at some frequency for the narrowband ANC systems. This paper uses the relationship of signal phasors to illustrate geometrically the operation and the behavior of two-tap adaptive filters. In addition, the best signal basis is therefore suggested to achieve a better performance from the viewpoint of phasor synthesis. Simulation results show that the well-selected signal basis not only achieves a better convergence performance but also speeds up the convergence for narrowband ANC systems