透過地震引致異常水文現象為了解水文地質特性的有效方法，而水文地質資料的完整性也是地震水文研究的關鍵。本研究蒐集2016高雄美濃地震震後地表與地下水文變化情形，嘗試理解地震引致台灣南部地區水文變化的機制。藉由分析第一含水層之同震水位變化之空間分布，以及地表破裂與液化噴砂之位置，可以發現同震水位變化主要發生在震央西北部的嘉南平原，而許多的液化與破裂點位位於新化斷層沿線。將液化點位與尖峰地動加速度與尖峰地動速度(PGA,PGV)的內插結果進行比較，結果顯示液化事件與PGV之關聯性較高。細究其數值則顯示引發液化事件之PGA門檻值約為150 cm/s^2，而PGV之門檻值約為40 cm/s。另外，新化斷層周圍數個地下水井中，部分深部含水層井位觀測到的水位變化不同於其他嘉南平原之水井呈現整體水位上升的情形，反而顯示同震水位下降，其位於淺部含水層的井位則顯示同震水位上升。其中，新化與那菝兩井顯示出不同深度的地下水位於震後變得靠近的現象，可能為不同含水層在震後變得連通而產生垂向的水壓傳遞所致。而我們對於含水層間連通性變化的推測，可以藉由以地潮分析不同含水層地下水位得出的相位差結果驗證，並且估算震前與震後含水層之導水係數變化情形，以此探討地震對於區域含水層的影響。結果顯示，新化井不同深度含水層之相位差變化趨勢於震後變得相似，代表新化井不同深度之含水層於地震後因裂隙而產生垂向連通，並引起地下水位變得相近。

The observations of hydrological anomalies induced by earthquakes are valuable data to investigate the hydrogeological properties. In this research, we collected the hydrological data before and after the Mw 6.4 2016 Meinong Earthquake. The main purpose is to investigate the mechanism of hydrological changes triggered by earthquakes. From the distribution of groundwater level changes at the first aquifer, as well as the distributions of the surface rupture and liquefaction points, it is found that the co-seismic groundwater level change is large in Chianan Plain, in the northwest area of the epicenter, and accompanied with a lot of ruptures and liquefactions located along the Hsinhua Fault. We compared the liquefaction points with the interpolated values of peak ground acceleration (PGA) and peak ground velocity (PGV) data, the result shows that the distribution of liquefaction points have the similar pattern with that of PGV values. The minimum threshold values of PGA and PGV for earthquake induced liquefaction are about 150 cm/s^2 and 40 cm/s, respectively. By the way, the observations in some wells in the deeper aquifer around the Hsinhua Fault show a different groundwater level change compared with the other wells in Chianan Plain. These wells show groundwater level decreases in the deep aquifer and increases in the shallow aquifer. In these wells, the Naba and Hsinhua wells show groundwater level convergence at different depths after the Meinong Earthquake. The earthquake enhances the connectivity between different aquifers and produces a vertical pressure propagation, that might be one possible mechanism for this phenomenon. The hypothesis of connectivity changes between different aquifers can be verified by analyzing the tidal response in different aquifers. Tidal analysis uses the phase shift pattern to judge if the aquifer permeability and transmissivity were changed after earthquakes, which is an important clue to understand how earthquake influences the hydrogeological properties. The results show that the pattern of phase shift at the Hsinhua well in different aquifers become similar, which is the evidence in proving the connection between different aquifers.

[1] Cooper Jr, H. H., Bredehoeft, J. D., Papadopulos, I. S., & Bennett, R. R., "The response of well‐aquifer systems to seismic waves", Journal of Geophysical Research, 70(16), 3915-3926, 1965.

[2] Hsieh, P. A., Bredehoeft, J. D., & Farr, J. M., "Determination of aquifer transmissivity from Earth tide analysis", Water Resources Research, 23(10), 1824-1832, 1987.

[3] Wang, C. Y., Liao, X., Wang, L. P., Wang, C. H., & Manga, M., "Large earthquakes create vertical permeability by breaching aquitards", Water Resources Research, 52(8), 5923-5937, 2016.

[4] Eaton, J., & Takasaki, K., "Seismological interpretation of earthquake-induced water-level fluctuations in wells", Bulletin of the Seismological Society of America, 49(3), 227-245, 1959.

[5] 賴文基，「地震引致地下水位變化機制之研究」，國立成功大學，博士論文，2010。

[6] Wakita, H., "Water wells as possible indicators of tectonic strain", Science, 189(4202), 553-555, 1975.

[7] Roeloffs, E., "Poroelastic techniques in the study of earthquake-related hydrologic phenomena", Advances in geophysics, 37, 135-195, 1996.

[8] Jónsson, S., Segall, P., Pedersen, R., & Björnsson, G., "Post-earthquake ground movements correlated to pore-pressure transients", Nature, 424(6945), 179-183, 2003.

[9] Chia, Y., Chiu, J. J., Chiang, Y.-H., Lee, T.-P., Wu, Y.-M., & Horng, M.-J., "Implications of coseismic groundwater level changes observed at multiple-well monitoring stations", Geophysical Journal International, 172(1), 293-301, 2008.

[10] Rice, J. R., & Cleary, M. P., "Some basic stress diffusion solutions for fluid‐saturated elastic porous media with compressible constituents", Reviews of Geophysics, 14(2), 227-241, 1976.

[11] Vucetic, M., "Cyclic threshold shear strains in soils", Journal of Geotechnical engineering, 120(12), 2208-2228, 1994.

[12] Hsu, C.-C., & Vucetic, M., "Volumetric threshold shear strain for cyclic settlement", Journal of geotechnical geoenvironmental engineering, 130(1), 58-70, 2004.

[13] Brodsky, E. E., Roeloffs, E., Woodcock, D., Gall, I., & Manga, M., "A mechanism for sustained groundwater pressure changes induced by distant earthquakes", Journal of Geophysical Research: Solid Earth, 108(B8), 2003.

[14] Kinoshita, C., Kano, Y., & Ito, H., "Shallow crustal permeability enhancement in central Japan due to the 2011 Tohoku earthquake", Geophysical Research Letters, 42(3), 773-780, 2015.

[15] Wang, C.-Y., & Manga, M., Earthquakes And Water. Springer, Berlin, 2009.

[16] Wang, C.-Y., Cheng, L.-H., Chin, C.-V., & Yu, S.-B., "Coseismic hydrologic response of an alluvial fan to the 1999 Chi-Chi earthquake, Taiwan", Geology, 29(9), 831-834, 2001.

[17] Rojstaczer, S., & Wolf, S., "Permeability changes associated with large earthquakes: An example from Loma Prieta, California", Geology, 20(3), 211-214, 1992.

[18] Muir‐Wood, R., & King, G. C., "Hydrological signatures of earthquake strain", Journal of Geophysical Research: Solid Earth, 98(B12), 22035-22068, 1993.

[19] Wang, C.-Y., Wang, C.-H., & Manga, M., "Coseismic release of water from mountains: Evidence from the 1999 (Mw= 7.5) Chi-Chi, Taiwan, earthquake", Geology, 32(9), 769-772, 2004.

[20] King, C.-Y., & Chia, Y., "Anomalous streamflow and groundwater-level changes before the 1999 M7. 6 Chi–Chi Earthquake in Taiwan: Possible mechanisms", Pure Applied Geophysics, 175(7), 2435-2444, 2018.

[21] Briggs, R. O., "Effects of Loma Prieta earthquake on surface waters in Waddell Valley 1", Journal of the American Water Resources Association, 27(6), 991-999, 1991.

[22] Tokunaga, T., "Modeling of earthquake-induced hydrological changes and possible permeability enhancement due to the 17 January 1995 Kobe Earthquake, Japan", Journal of Hydrology, 223(3-4), 221-229, 1999.

[23] Manga, M., "Origin of postseismic streamflow changes inferred from baseflow recession and magnitude‐distance relations", Geophysical Research Letters, 28(10), 2133-2136, 2001.

[24] Montgomery, D. R., & Manga, M., "Streamflow and water well responses to earthquakes", Science, 300(5628), 2047-2049, 2003.

[25] 馬國鳳，「台灣地震科學中心十周年記者會討論」，2015。

[26] Wu, B. R., Huang, M. W., Ke, S. S., & Lee, W. S., "Mesh-Based soil liquefaction analysis for emergency response-case study of the Meinong earthquake in Taiwan", 2017.

[27] 台灣地區寬頻地震網， http://bats.earth.sinica.edu.tw/.

[28] 中央氣象局地震測報中心， https://scweb.cwb.gov.tw/.

[29] 中央地質調查所，20160206地震地質調查報告，2016。

[30] 國家災害防救科技中心、國家地震工程研究中心，0206地震災情彙整與實地調查報告，2016。

[31] 中央地質調查所土壤液化潛勢查詢系統， https://www.liquid.net.tw/cgs/public/index.html.

[32] Lu, C.-C., Hwang, J.-H., & Hsu, S.-Y., "The impact evaluation of soil liquefaction on low-rise building in the Meinong earthquake", Earth, Planets Space, 69(1), 109, 2017.

[33] 經濟部中央地質調查所，20100304地震地質調查報告，2010。

[34] 國立成功大學防災研究中心，0206美濃地震災害概況，2016。

[35] 陳文山、俞何興、俞震甫、鍾孫霖、林正洪、林啟文、游能悌、吳逸民和王國龍，台灣地質概論，中華民國地質學會，2016。

[36] 陳文山、黃能偉、楊志成，「台灣西南部更新世沉積層序特性與前陸盆地演化」，經濟部中央地質調查所特刊， 1-38頁，2011。

[37] 何春蓀，台灣地質概論: 台灣地質圖說明書，經濟部中央地質調查所，1994。

[38] 財團法人中興工程顧問社，「地下水水文地質與補注模式研究」—105 年度地下水主要補注區補充地質調查案，經濟部中央地質調查所，2016。

[39] 陳文山、楊志成、楊小青，「如何建立台灣海岸平原區地下晚第四紀沉積層的地層架構」，經濟部中央地質調查所特刊， 101-114頁，2009。

[40] 張麗旭、周敏和陳培源，「民國35年12月5日台南之地震」，台灣省地質調查所彙刊， 1947。

[41] 國立雲林科技大學水土資源及防災科技研究中心，台灣地區地下水觀測網整體計畫成果彙編(81~105)，2017。

[42] 張健財、余貴坤，地下水水位變化與地震的關連性研究(Ⅲ)，2012。

[43] Doodson, A. T., "VI. The analysis of tidal observations", Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character, 227(647-658), 223-279, 1928.

[44] 黃瓊珠、李汴軍和高家俊，「天文潮位資料補遺之探討」，氣象學報， 46(2)， 15-28頁，2006。

[45] Cutillo, P. A., & Bredehoeft, J. D., "Estimating aquifer properties from the water level response to earth tides", Groundwater, 49(4), 600-610, 2011.

[46] Bredehoeft, J. D., "Response of well‐aquifer systems to earth tides", Journal of Geophysical Research, 72(12), 3075-3087, 1967.

[47] Hsieh, P. A., Bredehoeft, J. D., & Rojstaczer, S. A., "Response of well aquifer systems to earth tides: Problem revisited", Water Resources Research, 24(3), 468-472, 1988.

[48] Allègre, V., Brodsky, E. E., Xue, L., Nale, S. M., Parker, B. L., & Cherry, J. A., "Using earth‐tide induced water pressure changes to measure in situ permeability: A comparison with long‐term pumping tests", Water Resources Research, 52(4), 3113-3126, 2016.

[49] 逸奇資訊有限公司，地下水觀測與地質資料檢討分析水文地質參數-以屏東平原為例，經濟部水利署，2016。

[50] Tamura, Y., Sato, T., Ooe, M., & Ishiguro, M., "A procedure for tidal analysis with a Bayesian information criterion", Geophysical Journal International, 104(3), 507-516, 1991.

[51] Tamura, Y., & Agnew, D., "Baytap08 user's manual", 2008.

[52] 石黒真木夫、佐藤忠弘、田村良明、大江昌嗣, "地球潮汐デ-タ解析--プログラム BAYTAP の紹介", 統計数理研究所彙報, 32(1), 71-85, 1984.

[53] Elkhoury, J. E., Brodsky, E. E., & Agnew, D. C., "Seismic waves increase permeability", Nature, 441(7097), 1135-1138, 2006.

[54] Doan, M.-L., & Brodsky, E. E., "Tidal analysis of water level in continental boreholes A tutorial Version 2.2", 2006.

[55] 産業技術総合研究所， https://gbank.gsj.jp/wellweb/GSJ/water/analysis/.

[56] Beaumont, C., & Berger, J., "An analysis of tidal strain observations from the United States of America: I. The laterally homogeneous tide", Bulletin of the Seismological Society of America, 65(6), 1613-1629, 1975.

[57] Matsumoto, N., & Roeloffs, E., "Hydrological response to earthquakes in the Haibara well, central Japan–II. Possible mechanism inferred from time-varying hydraulic properties", Geophysical Journal International, 155(3), 899-913, 2003.

[58] Jan, S., Chern, C. S., Wang, J., & Chao, S. Y., "The anomalous amplification of M2 tide in the Taiwan Strait", Geophysical Research Letters, 31(7), 2004.

[59] Shi, Z., & Wang, G., "Hydrological response to multiple large distant earthquakes in the Mile well, China", Journal of Geophysical Research: Earth Surface, 119(11), 2448-2459, 2014.

[60] Shi, Y., Liao, X., Zhang, D., & Liu, C. P., "Seismic waves could decrease the permeability of the shallow crust", Geophysical Research Letters, 46(12), 6371-6377, 2019.

[61] Lai, W.-C., Hsu, K.-C., Shieh, C.-L., Lee, Y.-P., Chung, K.-C., Koizumi, N., & Matsumoto, N., "Evaluation of the effects of ground shaking and static volumetric strain change on earthquake-related groundwater level changes in Taiwan", Earth, planets and Space, 62(4), 391-400, 2010.

[62] Wang, C.-Y., Wong, A., Dreger, D. S., & Manga, M., "Liquefaction limit during earthquakes and underground explosions: implications on ground-motion attenuation", Bulletin of the Seismological Society of America, 96(1), 355-363, 2006.

[63] Midorikawa, S., & Wakamatsu, K., "Intensity of earthquake ground motion at liquefied sites", Soils and Foundations, 28(2), 73-84, 1988.

[64] Wong, A., & Wang, C. Y., "Field relations between the spectral composition of ground motion and hydrological effects during the 1999 Chi‐Chi (Taiwan) earthquake", Journal of Geophysical Research: Solid Earth, 112(B10), 2007.

[65] Steketee, J. A., "On Volterra's dislocations in a semi-infinite elastic medium", Canadian Journal of Physics, 36(2), 192-205, 1958.

[66] Okada, Y., "Internal deformation due to shear and tensile faults in a half-space", Bulletin of the Seismological Society of America, 82(2), 1018-1040, 1992.

[67] Lee, S. J., Yeh, T. Y., & Lin, Y. Y., "Anomalously large ground motion in the 2016 ML 6.6 Meinong, Taiwan, earthquake: A synergy effect of source rupture and site amplification", Seismological Research Letters, 87(6), 1319-1326, 2016.

[68] Wen, S., Yeh, Y.-L., Chang, Y.-Z., & Chen, C.-H., "The seismogenic process of the 2016 Meinong earthquake, southwest Taiwan", Terrestrial, Atmospheric Oceanic Sciences, 28(5), 2017.

[69] Koizumi, N., Lai, W. C., Kitagawa, Y., & Matsumoto, N., "Comment on “Coseismic hydrological changes associated with dislocation of the September 21, 1999 Chichi earthquake, Taiwan” by Min Lee et al", Geophysical Research Letters, 31(13), 2004.