Changes in hot spring temperature and hydrogeology of the Alpine Fault hanging wall, New Zealand, induced by distal South Island earthquakes
Changes in hot spring temperature and hydrogeology of the Alpine Fault hanging wall, New Zealand, induced by distal South Island earthquakes
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DOI：
10.1111/gfl.12093
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发表时间：
2015-02-01
期刊：
影响因子：
1.7
通讯作者：
Teagle, D. A. H.
中科院分区：
文献类型：
--
作者：
Cox, S. C.;Menzies, C. D.;Teagle, D. A. H.
新西兰南阿尔卑斯山的温泉起源于流体渗透到阿尔卑斯断层快速隆起和挖掘所产生的热异常中。Copland温泉（43.629S, 169.946E）是温泉中流量最大、温度最高的温泉之一，以6 +/- 1lsec（-1）的速度释放出富含二氧化碳的56-58摄氏度的强烈气泡水。2009年的Mw7.8级Dusky Sound（峡湾）地震和2010年的Mw7.1级Darfield（坎特伯雷）地震，分别距离春天350公里和180公里，造成了大约1摄氏度的特征，冷却延迟了5天。在达菲尔德Mw7.1级地震后，测量了电导率的下降和pH值的增加。地震引起的Cl、Li、B、Na、K、Sr和Ba浓度的降低和SO4浓度的增加反映了地下浅层环流大气流体混合比例的增加。大约0.5% g峰值地面加速度（PGA）和/或0.05-0.10MPa动应力的振幅影响科普兰温泉温度，在2011年克赖斯特彻奇Mw6.3余震或其他小地震中没有响应。南阿尔卑斯山中部每隔1-10年就会超过这样的阈值。中场距离低震动强度（MM III-IV）和地震能量密度(约10（-1)Jm(-3)）下的特征冷却响应与频谱频率的变化无关，不需要震后恢复。观测到的温度和流体化学响应可以反映泉水附近片岩山裂缝渗透率的细微变化。cGPS记录的永久10(-7)-10（-6）应变反映了裂缝的打开或产生，使大量相对较冷的近地表地下水与上涌的热水混合。高寒断层上盘的活动变形、构造和地形应力使南阿尔卑斯热液系统特别容易受到地震诱发的瞬态渗透作用。
Thermal springs in the Southern Alps, New Zealand, originate through penetration of fluids into a thermal anomaly generated by rapid uplift and exhumation on the Alpine Fault. Copland hot spring (43.629S, 169.946E) is one of the most vigorously flowing, hottest of the springs, discharging strongly effervescent CO2-rich 56-58 degrees C water at 6 +/- 1lsec(-1). Shaking from the Mw7.8 Dusky Sound (Fiordland) 2009 and Mw7.1 Darfield (Canterbury) 2010 earthquakes, 350 and 180km from the spring, respectively, resulted in a characteristic approximately 1 degrees C delayed cooling over 5days. A decrease in conductivity and increase in pH were measured following the Mw7.1 Darfield earthquake. Earthquake-induced decreases in Cl, Li, B, Na, K, Sr and Ba concentrations and an increase in SO4 concentration reflect higher proportions of shallow-circulating meteoric fluid mixing in the subsurface. Shaking at amplitudes of approximately 0.5% g Peak Ground Acceleration (PGA) and/or 0.05-0.10MPa dynamic stress influences Copland hot spring temperature, which did not respond during the Mw6.3 Christchurch 2011 aftershock or other minor earthquakes. Such thresholds should be exceeded every 1-10years in the central Southern Alps. The characteristic cooling response at low shaking intensities (MM III-IV) and seismic energy densities (approximately 10(-1)Jm(-3)) from intermediate-field distances was independent of variations in spectral frequency, without the need for post-seismic recovery. Observed temperature and fluid chemistry responses are inferred to reflect subtle changes in the fracture permeability of schist mountains adjacent to the spring. Permanent 10(-7)-10(-6) strains recorded by cGPS reflect opening or generation of fractures, allowing greater quantities of relatively cool near-surface groundwater to mix with upwelling hot water. Active deformation, tectonic and topographic stress in the Alpine Fault hanging wall, where orographic rainfall, uplift and erosion are extreme, make the Southern Alps hydrothermal system particularly susceptible to earthquake-induced transient permeability.