Nannofossil Biochronology of Tephra Layers in Core MD972143,Benham Rise,Western Philippine Sea

The 1990-1997 annually surveyed GPS data from 36 stations and continuous data from 3 permanent stations in southwestern Taiwan are utilized to study the spatial and temporal variations of crustal strain in thearea.Moderate to remarkable contraction rates of 0.48-2.01 μ strain/yr in91°-135°are observed in the vicinity of the Chukou fault(CKF).The contraction rates decrease toward either the east or the west.Along the surfacetrace of the CKF,the strain rates of the northern segment are approximately at the same level,while that for the central and southern segmentsclearly increase toward the south.The temporal variations of crustal strainnear the CKF are quite uniform during the period from 1990 to 1997.Analyzing the repeated GPS data of a dense profile across the central segmentof 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.Theeast velocity components relative to Penghu increase dramatically from 2.6mm/yr near the western coast to 39.9 mm/yr in the foothill region to theeast of the CKF.These results indicate that crustal strain is accumulatingrapidly and that there is a very high possibility of a forthcoming majorearthquake in the Chianan area.The extremely high strain rates in thesouthern segment of the CKF may be caused by the aseismic slip on thefault,as the seismic activity here is insignificant.

並列關鍵字

Philippine Sea ； Volcanic Ash ； Pliocene ； Pleistocene ； Nannofossil

國際替代計量

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