• 作者： 馮至津; 蕭德瑯; 劉忠智; 蔡義本
• 作者服務機構： 中央研究院物理研究所地震組
• 中文摘要： 臺北盆地由於超抽地下水，引起地盤下陷，造成了諸多不良的後果。為了制定合理有效的對策，必須探查詳細可靠的地下地質資料。中央研究院物理研究所地震組接受臺北市政府之委託，在臺北市區進行震波測勘以暸解臺北盆地底岩以上沖積層的構造。本組在六十四年三月至十二月間，自行設計製造儀器，並完成了臺北市南區八個測點的探測工作，效果十分良好。 本次探測的主要發現，可歸納如下: 1.各測點表土層厚度介於1至5公尺，P波速度變化很大，由200公尺／秒至450公尺／秒。 2.表土層下松山層的厚度相當一致，而P波速度卻因粘土與砂質互層組成的比例不同，而有相當變化，砂質多者速度較快。 3林口層為臺北盆地之主要含水層，其厚度在各地有相當的變化，一般來說，底岩愈深處，林口層也愈厚。 4.底岩深度有相當的變化，在盆地東南角，可淺至90公尺，而在盆地中心。卻達到了250公尺。根據探測的結果，並可推斷在中和至青年公園間，底岩較為隆起，深度約為118公尺。
• 英文摘要： Releveling of bench marks in 1971 and 1973 indicates that subsidence of theland surface in the Taipei Basin has now exceeded 1.8 meters since 1957.It is generally known that the decline of pressure head in the confined aquiferwithin the Pleistocene formations is a major cause of the subsidence. In order tosensibly determine the causes, predict the extent, magnitude, and the rate offuture subsidence and formulate the measures for checking the subsidence oralleviating its adverse effects, it is essential to have reliable data concerningthe sturcture of the Quaternary formations lying unconformably over the Tertiarybedrock in the Taipei Basin. To meet this basic need a seismic exploration usingthe weight-drop technique has been carried out at eight points in the southeasterndistrict of Taipei City during 1975. The primary findings are summarized below. 1 .The Holocene alluvium layer near the surface has a thickness ranging from1 to 5 meters. Its P-wave velocity varies from about 200 m/s to 450 m/s. 2. The P-wave velocity of the Pleistocene Sungshan formation varies signifi-cantly from place to place even though its thickness is relatively uniform. Varia-tions of the P-wave velocity appears to result from different proportions of themuddy and sundy layers in the formation. 3. The upper gravel layer of the Pleistocene Linkou formation has a highlyvariable thickness. In some places near the southeastern edge of the basin, itmay be completely absent whereas in other places, notably closer to the center ofthe basin, it may be as thick as 60 meters. The thickness of the lower layer ofthe Linkou formation also varies from about 40 to 150 meters. 4. The depth to the Tertiary bedrock varies considerably from place to place.It appears to deepen from about 90 meters at the southeastern edge to about 250meters near the center of the Taipei Basin. A zone of relatively shallow bedrockappears to exist between the southern edge in Chungho and the Youth Park northof Yungho where the depth to the bedrock is estimated as 118 meters. These data are valuable not only for understanding the subsidence of the landsurface but also for investigating the dynamic stability and dynamic response ofthe Quaternary formations under strong seismic loading.
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