Title

臺灣車籠埔斷層鑽探計劃A井岩心之破裂能研究

Translated Titles

The study of fracture energy in TCDP Hole-A

DOI

10.6342/NTU.2008.01557

Authors

游艾琦

Key Words

車籠埔斷層 ; 破裂能 ; 斷層泥 ; 粒徑分佈 ; Chelungpu fault ; fracture energy ; fault gouge ; grain size distribution

PublicationName

臺灣大學地質科學研究所學位論文

Volume or Term/Year and Month of Publication

2008年

Academic Degree Category

碩士

Advisor

宋聖榮

Content Language

繁體中文

Chinese Abstract

由斷層作用所引發的地震,之所以會造成各種災害,是因為釋放之前所累積的應變能的結果,如果我們能對地震斷層所釋放的能量加以研究,應該可以進一步了解地震斷層的基本性質。在滑移弱化模型(slip-weakening model)中,一次地震所釋放的彈性應變能可以分為:破裂能(fracture energy, EG)、摩擦熱(frictional heat, EH)以及輻射能(radiated energy, ER)。破裂能為岩石產生一個新的破裂面所需要的能量;摩擦熱為斷層滑移時摩擦產生的熱能;輻射能則以地震波的方式呈現。其中,破裂能與輻射能僅占總能量的一小部份,但它們相對的大小卻是影響地震破裂力學的關鍵,一般以輻射效率(radiation efficiency, ηR)表示ηR = ER / (ER + EG)。而輻射效率值越高,代表該斷層成熟度越高,也代表其破壞性越大。 在脆性斷層中,普遍存在有粒徑減小與斷層泥生成的現象,而在發展成熟的斷層裡,大部份的滑移也都在斷層泥中發生,因此透過分析斷層泥的粒徑分佈,估算破裂能。臺灣車籠埔斷層鑽探計劃(Taiwan Chelungpu-fault drilling project, TCDP)於2004年起在台中大坑(DaKeng)地區,車籠埔斷層北段東方約2公里處,鑽取了兩口岩心,其中A井深度為2003公尺。由肉眼觀察A井岩心,車籠埔斷層帶之斷層中心約1公尺厚,破裂帶於上盤有數公尺厚,下盤則不到1公尺便進入圍岩;而在車籠埔斷層帶以上則觀察到許多小斷層分佈其中,斷層泥厚度僅有數公釐至數公分不等,且通常沒有破裂帶的構造。本研究利用粒徑分析儀與顯微鏡影像兩種方法,分析車籠埔斷層帶以及淺部小斷層帶的斷層泥粒徑分佈,並檢討兩種分析方法的優劣,最後估算並比較兩者的破裂能。 結果顯示,使用粒徑分析儀分析方法,除了實驗上的誤差較大之外,細顆粒的分散情形也不佳,因此建議單獨使用較高階的雷射散射粒徑分析儀,可以簡單快速地概估破裂能;而顯微鏡影像分析方法,可以得到顆粒的樣貌、分佈,以及微構造等資訊,藉由影像軟體更可以得到顆粒的面積、圓度、軸長比等資料,雖然影像中顆粒重疊會造成數量上的低估,但還是能準確地估算出破裂能。淺部小斷層帶各標本,每1公釐厚斷層泥每單位面積所需的破裂能為2.76E+04~4.95E+04Jm-2不等,全都小於車籠埔滑移帶(1.03E+05~1.44E+05Jm-2不等),推測可能是粒徑分析儀分析方法的低估,或者是這些小斷層帶是由潛移作用造成之故。計算出車籠埔斷層主要滑移帶中各層的總破裂能後(7.78E+05~2.12E+06Jm-2不等),如果知道該層發生了幾次地震,就可以推算出一次地震所釋放的破裂能;而估計出一次地震產生的斷層泥厚度,再乘上每1公釐厚斷層泥每單位面積所需的破裂能,也能得到該次地震所釋放的破裂能。

English Abstract

Slip-weakening model can be used to explain the relationship between energy budget and physical processes of earthquake slip. Based on the model, the elastic strain energy released during an earthquake is partitioned into the fracture energy (EG), frictional heat (EH), and radiation energy (ER). Although radiation energy and fracture energy only occupy the small portion of total elastic energy, their ratio is the main factor of controlling earthquake rupture dynamics, expressed by radiation efficiency ηR = ER / (ER + EG). Fracture energy is defined as the energy at rupture tips that is required to create a rupture surface and produce a breakdown in strength. It is common to observe the grain-size reduction associated with the development of fault gouge within seismogenic faults. Also, the major displacement along mature faults usually occurred within the fault gouge. Thus, by estimating the fracture energy from the grain size distribution of fault gouge of TCDP cores, it can provide insights into understanding of faulting dynamics of the Chi-Chi earthquake. TCDP retrieved cores from two holes around the Dakeng area in 2004-2005. From the hole-A core, the Chelungpu fault zone, which slipped during the Chi-Chi earthquake, occurs at 1111 m depth, consisting of a 1-m-thick fault core including 12-cm-thick primary slip zone and several meters thick of damaged zone. Above the fault, there are many small faults can also be observed. The fault gouge of these small faults is only several millimeters to several centimeters thick, and the damaged zone does not develop well. We analysed the grain size distribution of the small faults and the primary slip zone of Chelungpu fault using particle size analyser and microscope measurements, to estimate the fracture energy associated with the gouge development. The fracture energy per millimeter thick gouge of small faults ranges from 2.76E+04 to 4.95E+04 Jm-2 and is smaller than fracture energy per millimeter thick gouge of the primary slip zone of Chelungpu fault which ranges from 1.03E+05 to 1.44E+05 Jm-2. This difference could be explained by that underestimation of small grain size portion and/or experimental error from particle size analyser measurement or that these small faults are products of creeping. After estimating the total fracture energy of the primary slip zone of Chelungpu fault (7.78E+05 to 2.12E+06 Jm-2), we can calculate the fracture energy associated to a single earthquake.

Topic Category 基礎與應用科學 > 地球科學與地質學
理學院 > 地質科學研究所
Reference
  1. 中央氣象局 (1999),集集大地震網站報告。
    連結:
  2. Abe, S. and Mair, K. (2005), Grain fracture in 3D numerical simulations of granular shear. Geophysical Research Letters 32, L05305.
    連結:
  3. Chester, F. M., Evans, J. P. and Biegel, R. L. (1993), Internal structure and weakening mechanisms of the San Andreas Fault. Journal of Geophysical Research Solid Earth 98, 771–786.
    連結:
  4. Chester, J. S., Chester, F. M. and Kronenberg, A. K. (2005), Fracture surface energy of the Punchbowl Fault, San Andreas system. Nature 437, 133–136.
    連結:
  5. Evans, J. P. and Chester, F. M. (1995), Fluid-rock interaction in faults of the San Andreas system: Inferences from San Gabriel fault rock geochemistry and microstructures. Journal of Geophysical Research 100, No. B7, 13007–13020.
    連結:
  6. Goddard, J. and Evans, J. P. (1995), Chemical changes and fluid-rock interaction in faults of crystalline thrust sheets, northwestern Wyoming, U.S.A. Journal of Structural Geology 17, 533–547.
    連結:
  7. Hirono, T., Yeh, E. C., Lin, W., Sone, H., Mishima, T., Soh, W., Hashimoto, Y., Matsubayashi, O., Aoike, K., Ito, H., Kinoshita, M., Murayama, M., Song, S. R., Ma, K. F., Hung, J. H., Wang, C. Y., Tsai, Y. B., Kondo, T., Nishimura, M., Moriya, S., Tanaka, T., Fujiki, T., Maeda, L., Muraki, H., Kuramoto, T., Sugiyama, K. and Sugawara, T. (2007), Nondestructive continuous physical property measurements of core samples recovered from hole B, Taiwan Chelungpu-Fault Drilling Project. Journal of Geophysical Research 112, B07404.
    連結:
  8. Ho, C. S. (1986), A synthesis of the geologic evolution of Taiwan. Tectonophysics 125, 1–16.
    連結:
  9. Hung, J. H., Wu, Y. H., Yeh, E. C., Wu, J. C. and TCDP Scientific Party (2007), Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project. Terrestrial, Atmospheric and Oceanic Sciences 18, No. 2, 271–293.
    連結:
  10. Lin, A. (1999), Roundness of clasts in pseudotachylytes and cataclastic rocks as an indicator of frictional melting. Journal of Structural Geology 21, 473–478.
    連結:
  11. Lin, W., Matsubayashi, O., Yeh, E. C., Hirono, T., Tanikawa, W., Soh, W., Wang, C. Y., Song, S. R. and Murayama, M. (2007), Profiles of volumetric water content in fault zones retrieved from hole B of the Taiwan Chelungpu-fault Drilling Project (TCDP). Accepted to Geophysical Research Letters.
    連結:
  12. Ma, K. F., Tanaka, H., Song, S. R., Wang, C. Y., Hung, J. H., Tsai, Y. B., Mori, J., Song, Y. F., Yeh, E. C., Soh, W., Sone, H., Kuo, L. W. and Wu, H. Y. (2006), Slip zone and energetics of a large earthquake from the Taiwan Chelungpu-fault Drilling Project. Nature 444, 473–476.
    連結:
  13. Marone, C. and Scholz, C. H. (1989), Particle-size distribution and microstructures within simulated fault gouge. Journal of Structural Geology 11, 799−814.
    連結:
  14. McGarr, A., Spottiswoode, S. M. and Gay, N. C. (1979), Observations relevant to seismic driving stress, stress drop, and efficiency. Journal of Geophysical Research 84, 2251–2261.
    連結:
  15. Scholz, C. H. (1990), The Mechanics of Earthquakes and Faulting. Cambridge University Press, Cambridge, 439pp.
    連結:
  16. Sibson, R. H. (1977), Fault rocks and fault mechanisms. J. Geol. Soc. Lond. 133, 191–213.
    連結:
  17. Song, S. R., Kuo, L. W., Yeh, E. C., Wang, C. Y., Hung, J. H. and Ma, K. F. (2007), Characteristics of the Lithology, Fault-Related Rocks and Fault Zone Structures in TCDP Hole-A. Terrestrial, Atmospheric and Oceanic Sciences 18, No. 2, 243–269.
    連結:
  18. Tanaka, H., Fujimoto, K., Ohtani, T. and Ito, H. (2001), Structural and chemical characterization of shear zones in the freshly activated Nohima fault, Awaji Island, southwest Japan. Journal of Geophysical Research 106, No. B5, 8789–8810.
    連結:
  19. Teng, L. S. (1990), Geotectonic evolution of late Cenozoic arc-continent collision in Taiwan. Tectonophysics 183, 57–76.
    連結:
  20. Venkataraman, A. and Kanamori, H. (2004), Observational constraints on the fracture energy of subduction zone earthquakes. Journal of Geophysical Research 109, B05302.
    連結:
  21. Wilson, B., Dewers, T., Reches, Z. and Brune, J. (2005), Particle size and energetics of gouge from earthquake rupture zones. Nature 434, 749–752.
    連結:
  22. Yu, S. B., Chen, H. Y. and Kuo, L. C. (1997), Velocity field of GPS stations in the Taiwan area. Tectonophysics 274, 41–59.
    連結:
  23. 中央地質調查所 (2000),九二一地震地質調查報告。
  24. 中央地質調查所 (2000),九二一集集地震車籠埔斷層沿線地表破裂位置圖。
  25. 何春蓀 (1986),台灣地質概論台灣地質圖說明書。經濟部中央地質調查所,共163頁。
  26. 何信昌、陳勉銘 (2000),五萬分之一臺灣地質圖說明書圖幅第24號—臺中。經濟部中央地質調查所,共65頁。
  27. 陳文山、鄂忠信、陳勉銘、楊志成、張益生、劉聰桂、洪崇勝、謝凱旋、葉明官、吳榮章、柯炯德、林清正、黃能偉 (2000a),上一更新世臺灣西部前陸盆地的演化:沈積層序與沈積物組成的研究。經濟部中央地質調查所彙刊第十三號,137–156頁。
  28. Jeng, F. S., Hsiao, M. H. and Lu, C. Y. (1996), Numerical simulation of neotectonics near Peikang high. Journal of the Geological Society of China 39, No. 4, 557–578.
  29. Kanamori, H. and Heaton, T. H. (2000), Microscopic and macroscopic physics of earthquakes. Geocomplexity and the Physics of Earthquakes, Geophys. Monogr. Ser. 120, 147–163. (edited by Rundle, J. B., Turcotte, D. L. and Klein, W.) (AGU, Washington DC)
  30. Kuo, L., Song, S. and Chen, H. (2005), Characteristics of Clay Minerals in the Fault Zone of TCDP and its Implications, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract T43D-05.
  31. Lawn, B. (1993), Fracture of Brittle Solids 2nd edn. Cambridge University Press, New York, 378pp.
  32. Sammis, C. G., Osborne, R. H., Anderson, J. L., Banerdt, M. and White, P. (1986), Self-similar cataclasis in the formation of fault gouge. Pure and Applied Geophysics 124, 53−78.
Times Cited
  1. 陳佩竹(2011)。臺灣車籠埔斷層帶計算破裂能之最小顆粒。臺灣大學地質科學研究所學位論文。2011。1-78。 
  2. 周述蓉(2008)。科技考古:以中國東部史前遺址為例。臺灣大學地質科學研究所學位論文。2008。1-104。