本研究分析1991年1月至2002年2月間，車籠埔斷層下盤地區於集集地震前、後所發生之地震之型態與震源機制，發現該地區之地震成一西北-東南向，長約35公里、寬約8公里的帶狀分佈。其中，集集地震前，地震集中發生於集集主震震央西側約4公里處；而集集地震後，地震則集中於集集主震震央西北側10～20公里處。此外，無論集集地震發生前、後，地震事件均集中發生於兩個主要深度： 9~13km（淺部）以及17~27km（深部）內。

　　藉由地震事件之震源機制解與應力反演結果，我們得到以下結論：（1）車籠埔斷層下盤地區之地震活動與應力狀態主要受東-西向板塊壓縮應力的作用與原先存在之伸張構造系統所控制。（2）集集地震發生後，車籠埔斷層下盤地區之地震活動反應了區域性應力釋放的過程，並可利用應力軸轉換配合原先存在之斷層系統加以解釋其狀態。（3）車籠埔斷層下盤地區淺部地殼原先存在之構造可能包括位於地下10-11公里處之基底滑脫面，以及基底滑脫面上下受地殼彎曲張裂作用所產生之南-北向正斷層系統。

　　We analyze the seismicity pattern and style of earthquake faulting in the footwall of the Chelungpu fault before and after the 21 September l999 (local time) ML=7.3 Chi-Chi, Taiwan earthquake. The earthquakes analyzed occurred in a period between January 1991 and February 2002.

　　The relocated seismicity defines a NW-SE-trending lineament with its width and length of ~8 km and ~35 km, respectively. The seismicity are loosely separated by two clusters: one covers mainly the pre-Chi-Chi events located just ~4 km west of the Chi-Chi main shock, and the other contains mostly post-Chi-Chi events and is separated from the Chi-Chi main shock by 10-20 km. All events occurred before and after Chi-Chi earthquake are marked by two depth levels: one is a cluster of earthquakes in the depth range of 9-13 km, and the other includes earthquakes in the deeper zone spreading within 17-27 km depths.

　　According to the focal mechanisms and the stress inversion results, we suggested that: (1) The seismicity pattern and the state of stress in the footwall of the Chelungpu fault is characterized by local extensional stress system superimposed on regional stress regime resulted from plate convergence. (2) The mixed style of earthquake faulting observed in post-Chi-Chi events is mainly a manifestation of stress relaxation processes, and can be explained by an alternating stress permutation model with the inclusion of pre-existing fault systems. (3) The pre-existing fault systems in the shallow crust of the footwall of the Chelungpu fault may involve flexural extension processes on the detachment.

中文部分

中央氣象局，1999，集集大地震網站報告。

何春蓀，1988，臺灣地質概論/臺灣地質圖說明書，經濟部中央地質調查所，共118頁。

何美儀，1994，臺灣西部地區三維速度構造，國立中央大學地球物理研究所碩士論文，共125頁。

辛在勤、張建興、陳國誠，2000，由集集餘震資料探討滑脫面之運動，地震活動及地殼變形研討會論文集。

李錦發、賴典章、徐兆祥、李重毅、溫國樑，1997，臺灣中西部西北～東南向轉接斷層帶，中國地質學會八十六年年會大會手冊及論文摘要，第325-329頁。

李錦發、賴典章、林朝宗、李重毅、徐兆祥，1998，三義～東勢～埔里西北向地震密集帶的新期構造與運動特徵，第七屆臺灣地區地球物理研討會論文集，第451-458頁。

李錦發、林朝宗、賴典章、劉昭宏，2000，集集大地震地表破裂機制之探討，經濟部中央地質調查所特刊，12，第155-169頁。

林慶偉、劉彥求、賴文基、黃敏郎、謝正倫，2000，集集地震地表斷層特性及其轉折機制之探討，921集集大地震週年紀念學術研討會論文集，第43-61頁。

周穎蔚，1999，臺灣西部前陸盆地地體架構、彎曲隆起演化及彎曲張裂構造型態，國立臺灣大學海洋研究所博士論文，共125頁。

侯進雄、賴典章、費立沅、王菁穗、陳文和，2000，高精度測量在車籠埔活動斷層監測與調查上之應用研究-九二一地震前後測量結果比較，經濟部中央地質調查所特刊，12，第191-210頁。

徐兆祥、李重毅、李錦發，1996，臺灣中部苗栗-台中-南投地區西北-東南向地震帶之地體構造意義，「臺灣第四紀」第六次研討會暨「台北盆地地下地質與工程環境綜合調查研究」成果發表會論文集，第224-228頁。

徐兆祥、李重毅、李錦發、張渝龍、毛爾威，1997a，臺灣西北東南向平移斷層及其地體構造意義，中國地質學會八十六年年會大會手冊及論文摘要，第309-312頁。

徐兆祥、李重毅、張渝龍、毛爾威，1997b，臺灣西部的麓山帶，中國地質學會八十六年年會大會手冊及論文摘要，第318-321頁。

康耿豪、林泉家、紀立民、鄭錦桐、李錫堤，2000，921集集大地震的斷層分段與位移量分布特性，中國地質學會八十九年年會暨學術研討會大會手冊暨論文摘要，第141-143頁。

陳文山、陳于高、劉聰桂、黃偉能、林清正、宋時驊、李昆杰，2000，921集集地震的地震斷層特性，中國地質學會八十九年年會暨學術研討會大會手冊暨論文摘要，第5-8頁。

陳文山、黃柏壽、陳于高、宋國城、張徽正、李元希、李昆杰、楊志成、黃能偉、宋時驊、張憲卿、李龍昇，2001，集集地震斷層特性與構造環境的意義，中國地質學會九十年年會暨學術研討會大會手冊暨論文摘要，第3-5頁。

黃金來，1969，台中車籠埔區震測解釋報告，中國石油公司未刊報告，共17頁。

楊耿明、葉明官、吳榮章、丁信修，2000，彰化斷層及相關構造之幾何形貌、特性與演化，中國地質學會八十九年年會大會手冊及論文摘要，第103-105頁。

盧佳遇、朱傚祖、李建成、詹瑜璋、張國楨，2002，基磐型態對逆衝構造的影響—以1999集集地震為例，中國地質學會九十一年年會暨學術研討會論文摘要，第182-183頁。

經濟部中央地質調查所，2000，九二一地震地質調查報告。

英文部分

Aki, K., and P. G. Richards, 1980, Quantitative Seismology: Theory and Methods, W. H. Freeman and Company, San Francisco.

Angelier J., 1979, Determination of the mean principal direction of stresses for a given fault population, Tectonophys., 56, T17-T26.

Angelier J., 1984, Tectonic analysis of fault slip data sets, J. Geophys. Res., 89, p. 5835-5848.

Angelier J., H. T. Chu, J. C. Lee, J. C. Hu, F. Mouthereau, C. Y. Lu, B. Deffontaines, S. Lallemand, Y. B. Tsai, J. D. Chow, and D. Bureau, 2000, Geological knowledge and seismic risk mitigation: insights from the Chi-Chi earthquake, vol. І, edited by Loh C. H., and W. I. Liao, p. 13-24. Nat. Center for Research on Earthquake Engineering, Taipei.

Angelier J., J. C. Lee, H. T. Chu, J. C. Hu, C. Y. Lu, Y. C. Chan, T. J. Lin, Y. Font, B. Deffontaines, and Y. B. Tsai, 2001, The Chichi earthquake, 1999, and its role in the Taiwan orogen, Earth and Planetary Sciences, 333, p. 5-21.

Bradley, D. C., and W. S. F. Kidd, 1991, Flexural extension of the upper continental crust collisional foredeep, Bull. Seiemol. Soc. Am., 103, p. 1416-1438.

Chang, Stanley S. L., 1971, Subsurface Geologic Study of the Taichung Basin, Taiwan, Petro. Geol. Taiwan, 8, p. 21-45.

Chen, J. S., 1978, A comparative study of the refraction and reflection seismic data obtained on the Changhua plain to the Peikang shelf, Taiwan, Petro. Geol. Taiwan, 15, p. 199-217.

Dahlen, F. A., J. Suppe, and D. M. Davis, 1984, Mechanics of fold-and-thrust belts and accretionary wedge: cohesive Coulomb theory, J. Geophys. Res., 89, p. 10,087-10,101.

Das, S., and C. H. Scholz, 1981, Off-fault aftershock clusters caused by shear stress increase? Bull. Seiemol. Soc. Am., 71, p. 1669-1675.

Deffontaines, B., O. Lacombe, J. Angelier, H. T. Chu, F. Mouthereau, C. T. Lee, J. Deramond, J. F. Lee, M. S. Yu, and P. M. Liew, 1997, Quaternary transfer faulting in the Taiwan Foothills: evidence from a multisource approach, Tectonophys., 274, p. 61-82.

Deramond, J., P. Souquet, B. Delcaillau, J. Angelier, H. T. Chu, J. F. Lee, T. Q. Lee, P. M. Liew, T. S. Lin, and L. Teng, 1995, Determining the collision belt evolution from foreland tectonic-sedimentary record. A case history: The Foothills of Taiwan, Program and extended abstracts, Active Collision in Taiwan, 3rd Sino-French Symposium, p. 94-104.

Efron, B., and R. Tibshirani, 1986, Bootstrap methods for standard errors, confidence intervals, and other measures of statistical accuracy, Stat. Sci., 1, p. 54-77.

Elishewitz, B., 1963, A new interpretation of the structure of the Miaoli area in the light of the decollement tectonics of northern Taiwan, Petro. Geol. Taiwan, 2, p. 21-45.

Ellsworth, W. L., 1982, A general theory for determining state of stress in the earth from fault slip measurements, Terrea Cognita, 2, p. 170-171.

Ellsworth, W. L. and X. Zhonghuai, 1980, Determination of the stress tensor from focal mechanism data, abstract, Eos Trans. AGU, 61, p.1117.

Engdahl, E. R., S. Billington, and C. Kisslinger, 1989, Teleseismically record seismicity before and after the May 7, 1986, Andreanof Islands, Alaska, earthquake, J. Geophys. Res., 94, p. 15,481-15,498.

Gephart, J. W., FMSI, 1990a, A Fortran program for inverting fault/slickenside and earthquake focal mechanism data to obtain the regional stress tensor, Comput. And Geosci., 16, p. 953-989.

Gephart, J. W., 1990b, Stress and the direction of slip on fault planes, Tectonics, 9, p. 845-858.

Gephart, J. W., and D. W. Forsyth, 1984, An improved method for determining the regional stress tensor using earthquake focal mechanism data: application to the San Fernando earthquake sequence. J. Geophys. Res., 100, p. 22,197-22,213.

Gomberg, J. S., K. M. Shedlock, and S. W. Roecker, 1990, The effect of S-wave arrival times on the accuracy of hypocenter estimation, Bull. Seiemol. Soc. Am., 80, p. 1605-1628.

Hardebeck J. L., and E. Hauksson, 2001, Stress orientations obtained from earthquake focal mechanisms: what are the appropriate uncertainty estimates? Bull. Seiemol. Soc. Am., 91, p. 250-262.

Hu, J. -C., and J. Angelier, 2001, 3-D distinct element analysis accounts for stress permutations in brittle tectonics, Program Proceeding of 2001 Joint Geosciences Assembly, p. 60-61.

Jackson, M., and R. Bilham, 1994, Constraints on Himalayan deformation inferred from vertical velocity fields in Nepal and Tibet, J. Geophys. Res., 99, p. 13,897-13,912.

Jouanne, F., G. Menard, and X. Darmendrail, 1995, Present-day vertical displacements in the north-western Alps and southern Jura Mountains; data from leveling comparisons, Tectonics, 14, p. 606-616.

Kao, H., 2002, Seismogenic patterns of the 1999 Chi-Chi, Taiwan, earthquake sequence: Source parameters of aftershocks and tectonic implications on orogeny, submitted to J. Geophys. Res.

Kao, H., and J. Angelier, 2001a, The Chichi earthquake sequence, Taiwan: results from source parameter and stress tensor inversions, Earth and Planetary Sciences, 333, p. 65-80.

Kao, H., and J. Angelier, 2001b, Stress tensor inversion for the Chi-Chi earthquake sequence and its implications on regional collision, Bull. Seismol. Soc. Am., 91(5), p. 1028-1040.

Kao, H., and W. P. Chen, 2000, The Chi-Chi earthquake sequence: Active, out-of-sequence thrust faulting in Taiwan, Science, 288, p. 2346- 2349.

Kao, H., Y. H. Liu, W. T. Liang, and W. P. Chen, 2002, Source parameters of regional earthquakes in Taiwan (1999-2000) and data release note for the Chi-Chi earthquake sequence from BATS, submitted to TAO.

King, G. C. P., R. S. Stein, J. Lin, 1994, Static stress changes and the triggering of earthquakes, Bull. Seismol. Soc. Am., 84, p. 935-953.

Kissling E., W. L. Ellsworth, D. Eberhart-Phillip, and U. Kradolfer, 1994, Initial reference models in local earthquake tomography, J. Geophys. Res., 99, p. 19,635-19,646.

Kisslinger, C., 1980, Evaluation of S to P amplitude ratios for determining focal mechanisms from regional network observations, Bull. Seismol. Soc. Am., 70(4), p. 999-1014.

Kisslinger, C., J. R. Bowman, and K. Koch, 1981, Procedures for computing focal mechanisms from regional network observations, Bull. Seismol. Soc. Am., 70, p. 999 – 1014.

Lee J. C., H. T. Chu, J. Angelier, Y. C. Chan, J. C. Hu, Y. L. Chia, R. J. Rau, 2002, Geometry and structure of northern surface ruptures of the 1999 Mw=7.6 Chi-Chi earthquake: influence from inherited fold belt structure, J. Struc. Geol., 24, p. 173-192.

Lee S. J., and K. F. Ma, 2000, Rupture process of the 1999 Chi-Chi, Taiwan, earthquake from the inversion of teleseismic data, TAO, 11, p. 591-608.

Lin. C. H., 2001, The 1999 Taiwan earthquake: a proposed stress-focusing, heel-shaped model, Bull. Seismol. Soc. Am., 91, p. 1053-1061.

Lu, C. Y., 1994, Neotectonics in the foreland thrust belt of Taiwan, Petro. Geol. Taiwan, 29, p. 1-26.

Lu, C. Y., and K. J. Hsu, 1992, Tectonic evolution of the Taiwan mountain belt, Petro. Geol. Taiwan, 27, p. 21-46.

Ma, K., and J. Mori, 2000, Rupture process of the 1999 Chi-Chi, Taiwan earthquake from direct observatios and joint inversion of strong motion, GPS and teleseismic data, EOS Tran. Am. Geophys. Union 81, WP104.

McKenzie, D. P., 1969, The relation between fault plane solutions and the directions of the principal stress, Bull. Seismol. Soc. Am., 59, p. 591-601.

Michael, A. J. , 1984, Determination of stress from slip data: faults and fold, J. Geophys. Res., 89, p. 11,517 – 11,526.

Michael, A. J., 1987a, Use of focal mechanisms to determine stress: a control study, J. Geophys. Res., 92, p. 357-368.

Michael, A. J., 1987b, Stress rotation during the Coalinga aftershock sequence, J. Geophys. Res., 92, p. 7963 – 7979.

Mouthereau, F., O. Lacombe, B. Deffontaines, J. Angelier, H. T. Chu, and C. T. Lee, 1999, Quaternary transfer faulting and belt front deformation at Pakuashan (western Taiwan), Tectonics, 18(2), p. 215-230.

Mouthereau, F., J. Angelier, and C. T. Lee, 2002, The 21-September-1999 earthquake: structural inheritance and basement involvement at the front of the Taiwan mountain, Earth and Planetary Sciences, 333, p. 93-103.

Pan, Y. S., 1967, Interpretation and seismic coordination of the Bouguer gravity anomalies over west-central Taiwan, Petro. Geol. Taiwan, 5, p.99-115.

Pavlis, G. L., 1986, Appraising earthquake hypocenter location errors: a complete, practical approach for single-event location, Bull. Seismol. Soc. Am., 76, p. 1699-1717.

Rau, R. J., 1996, 3-D tomography, focal mechanisms, and Taiwan orogeny, Ph. D. Thesis, 222 pp.

Rau, R. J. and Wu, F. T. , 1998, Active tectonic Taiwan orogeny from focal mechanisms of small-to-moderate-sized earthquakes, TAO., 9(4), p. 755 – 778.

Rau, R. J., F. T. Wu, and T. C. Shin, 1996, Regional network focal mechanism determination using 3-D velocity model and SH/P amplitude ratio, Bull. Seismol. Soc. Am., 86, p. 1270-1283.

Reasenberg, P. A., and R. W. Simpson, 1992, Response of regional seismicity to the static stress change produced by the Loma Prieta earthquake, Science, 255, p. 1687-1690.

Seno, T, 1977, The instantaneous rotation vector of the Philippine sea plate relative to the Eurasian plate, Tectonophys., 42, p. 209-226.

Shin, T. C., 1993, The caculation of local magnitude from the simulated Wood-Anderson seismograms of the short-period seismograms in the Taiwan area, TAO, 4, p. 155-170.

Snoke, J. A., J. W. Munsey, A. G. Teague, and G. A. Bollinger, 1984, A program for focal mechanism determination by combined use of polarity and SV-P amplitude ratio data, Earthquake Notes, 55(3), p. 15.

Suppe, J, 1980a, A retro deformable cross section of north Taiwan, Proc. Geo. Soc. China, 23, p. 46-55.

Suppe, J, 1980b, Imbricated structure of western foothills belt, south centeral Taiwan, Petro. Geol. Taiwan, 17, p. 1-16.

Suppe, J, 1987, The active Taiwan mountain belt, in The Anatomy of Mountain Ranges, edited by J. P. Schaer and J. Rodgers, p.277-293., Princeton Univ. Press, Princeton.

Waldhauser, F. and Ellsworth, L., 2000, A double-difference earthquake location algorithm: method and application to the northern Hayward Fault, California, Bull. Seism. Soc. Am, 90, p. 1353 – 1368.

Wang, C. Y., and T. C. Shin, 1998, Illustrating 100 years of Taiwan seismicity, TAO, 9, p. 589-614.

Wang, C. Y., C. H. Chang, and H. Y. Yen, 2000, An interpretation of the 1999 Chi-Chi earthquake in Taiwan Based on the thin-skinned thrust model, TAO, 11, p. 609-630.

Wu F. T., R. J. Rau, and D. Salzberg, 1997, Taiwan orogeny: thin-skinned or lithospheric collision?, Tectonophys., 274, p. 191-220.

Yang, M., R. J. Rau, J. Y. Yu, and T. T. Yu, 2000, Geodetically observed surface displacements of the 1999 Chi-Chi, Taiwan, earthquake, Earth, Planets and Space, 52, p. 403-413.

Zoback, M. L. 1992, First- and second-order patterns of stress in the lithosphere: The world stress map project, J. Geophys. Res., 97, p. 11,703-11,728.