Acoustic emission source parameters of laboratory triaxial stick-slip experiments on two Westerly granite samples

These data are supplementary to the GJI research article of Blanke et al. 2020, in which static stress drop estimates of laboratory acoustic emission (AE) waveform records were analyzed. Stick-slip experiments were conducted on two triaxial loaded Westerly Granite samples of different roughness: 1) a smooth saw-cut fault (sample S12) and 2) a rough fault (sample W5). Both experiments resulted in six stick-slip failures of which five were analyzed for each fault. A variant of the spectral ratio technique was applied to find the best fitting source parameters. Laboratory Experiments: Acoustic emission waveform data of two triaxial stick-slip experiments was recorded at room temperature on cylindrical oven-dried Westerly Granite samples of 105-107 mm height and 40-50 mm diameter. The experiments were conducted on a smooth saw-cut (sample S12) and a rough fault (sample W5). Both experiments were performed in a servo-controlled MTS loading frame equipped with a pressure vessel. The acoustic emission activity was monitored by 16 piezoceramic transducers with a resonance frequency of about 2 MHz. A transient recording system (DAX-Box, Prökel, Germany) recorded full waveform data in triggered mode at a sampling frequency of 10 MHz and an amplitude resolution of 16 bits. The rough fault W5 was first prepared with Teflon-filled saw-cut notches at 30° inclination to the vertical axis and then fractured at 75 MPa. Then, each sample, S12 and W5, was subjected to constant confining pressure of 133 MPa and 150 MPa and then loaded in axial compression using a strain rate of 3*10-4 mm/s and 3*10-6 mm/s, respectively. Data description: The tables 2020-008_Blanke-et-al_S1_S12.txt and 2020-008_Blanke-et-al_S2_W5.txt contain AE locations and occurrence, and source parameter estimates of the smooth fault S12 and the rough fault W5, respectively. Both column headers show coordinates of AE locations (X, Y, Z [mm]), temporal occurrence (t [sec]), seismic moment (M0 [Nm]), corner frequency (f0 [Hz]), source radius (r [mm]), static stress drop (stress drop [MPa]), and moment magnitude (MW). M0 and f0 were estimated from the amplitude spectra, using the spectral ratio technique. The source radii were calculated for S-waves using the dynamic circular source model of Madariaga (1976). Static stress drops were estimated following Eshelby (1957). Both tables are used and displayed in Blanke et al. (2020).

本数据集为Blanke等人2020年发表于《GJI》的研究论文的补充数据，该研究分析了实验室声发射（Acoustic Emission, AE）波形记录的静态应力降（static stress drop）估算结果。

粘滑试验（stick-slip experiments）针对两个不同粗糙度的三轴加载西利花岗岩（Westerly Granite）试样开展，分别为：1）光滑锯切断层试样（S12）；2）粗糙断层试样（W5）。两组试验均产生6次粘滑破坏，其中各选取5次破坏进行分析。研究采用改进的频谱比技术（spectral ratio technique）以获取最优拟合的震源参数。

实验室实验细节：本数据集包含两组三轴粘滑试验的声发射波形数据，试验于室温下开展，试样为经烘箱干燥的圆柱形西利花岗岩，高度105~107 mm，直径40~50 mm。试验分别针对光滑锯切断层试样S12与粗糙断层试样W5进行，加载系统采用配备压力舱的伺服控制MTS加载架。通过16个谐振频率约2 MHz的压电陶瓷换能器监测声发射活动。瞬态记录系统（DAX-Box，德国Prökel公司）以触发模式采集完整波形数据，采样频率10 MHz，幅度分辨率16 bit。

粗糙断层W5的制备与加载流程：首先制备与竖直轴呈30°倾角的特氟龙填充锯切切口，随后在75 MPa压力下发生断裂。随后分别对S12与W5试样施加恒定围压：S12围压133 MPa，W5围压150 MPa；随后分别以3×10^-4 mm/s与3×10^-6 mm/s的应变速率进行轴向压缩加载。

数据描述：文件2020-008_Blanke-et-al_S1_S12.txt与2020-008_Blanke-et-al_S2_W5.txt分别存储了光滑断层S12与粗糙断层W5的声发射定位结果、发生时刻信息以及震源参数估算值。两个文件的列标题均包含：声发射定位坐标（X、Y、Z，单位：mm）、时间发生时刻（t，单位：秒）、地震矩（M0，单位：牛·米）、拐角频率（f0，单位：赫兹）、震源半径（r，单位：mm）、静态应力降（stress drop，单位：兆帕）以及矩震级（MW）。其中M0与f0通过频谱比技术由振幅谱估算得到；震源半径基于Madariaga（1976）提出的动态圆形震源模型，针对S波计算得出；静态应力降则依据Eshelby（1957）的方法估算。上述两个表格的数据已在Blanke等人2020年的研究中使用并展示。