Research on the difference of noise characteristics before and after earthquake based on GPS time series analysis
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摘要: 针对现有地震预测研究中噪声特性分析研究较少,就较大地震对GPS时间序列噪声特性的影响进行分析. 选取较大地震及相应的临近测站,将GPS时间序列按照时间跨度分为震前4~3 a、前3~2 a、前1~0 a、震后0~1 a、后1~2 a五个时段,分别求取各时段的谱指数,采用不同的噪声模型组合对它们进行噪声特性分析,然后对结果进行对比. 结果表明:地震前后谱指数、速度场、振幅相位等变化较大,GPS时间序列噪声特性对地震响应明显;部分测站地震前后谱指数、速度场、周年振幅等较震前1~0 a具有一致性;地震孕育阶段,闪烁噪声+白噪声(FN+WN)在所有最优噪声模型中所占比例上升,闪烁噪声+随机漫步噪声+白噪声(FN+RWN+WN)中FN在所有噪声分量中所占比例上升,震后均下降,与地震时能量释放,地震后站点运动态势恢复常态相一致.Abstract: According to the fact that there is no enough research of the noise characteristics in the study of earthquake prediction, this paper analyze the influence of large earthquake on the noise characteristics of time series. Focusing on the large earthquake and the corresponding station nearby, the GPS time series were separated to five periods, before the earthquake 4~3 years, 3~2 years, 1~0 years, after the earthquake 0~1 years and 1~2 years. The spectral index of each period. Noise analysis was implemented using different noise model combination. Analysis results shows that, the change of spectral index, velocity field, amplitude and phase before and after the earthquake is very big, and the noise characteristics of GPS time series are significant to seismic response; For part of the stations the spectral index, velocity field and anniversary amplitude before and after the earthquake is consistent compare with results of the 1~0 years before the earthquake. In earthquake incubation period, the proportion of flicker noise + white noise(FN+WN) increased. And the noise component FN in flicker noise + random walk noise+ white noise(FN+RWN+WN) increased among all the noise components. All the ratio decreased after the earthquake, which is in consistent of the earthquake energy releaseand restoration of the site more meat situation to normal status after the earthquake.
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表 1 较大地震及相应测站信息
地震时间 经/纬度/(°) 震级 震源深度/km 临近测站 地震和测站距离/km Offset(阶跃) 2001.4781 −72.71/−17.28 8.4 29.6 AREQ 160 有 2009.7438 −171.97/−15.13 8.1 12.0 ASPA 160 有 2000.4658 97.17/−13.47 7.9 15.0 COCO 140 有 2010.1575 −73.15/−35.98 8.8 23.2 CONZ 130 有 2002.3164 144.67/13.15 7.0 69.1 GUAM 50 有 2008.2828 158.49/−55.56 7.1 22.0 MAC1 120 无 2008.4522 140.85/39.03 6.9 12.0 MIZU 33 有 2011.1904 141.38/35.92 7.9 29.0 TSKB 140 有 表 2 GPS时间序列分段概况
测站 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ 1997.4781—1998.4753 1998.4781—1999.4753 2000.4795—2001.4753 2001.5301—2002.2397 2002.6260—2003.5301 ASPA 2005.7438—2006.7411 2006.7438—2007.7411 2008.8566—2009.7411 COCO 1996.4658—1997.4644 1997.4671—1998.4644 1999.4671—2000.4631 2000.4686—2001.4616 2001.4726—2002.4671 CONZ 2006.1575—2007.1548 2007.1575—2008.1571 2009.1603—2010.1548 GUAM 1998.3164—1999.3137 1999.3164—2000.3156 2001.3164—2002.3137 2002.3192—2003.3137 2003.3164—2004.3183 MAC1 2005.2836—2006.2808 2007.2836—2008.2801 2008.2855—2009.2397 2009.3055—2010.2836 MIZU 2007.4534—2008.4495 2008.4549—2009.4507 2009.4534—2010.4534 TSKB 2007.1904—2008.1899 2008.1926-2009.1904 2010.1904—2011.1877 2011.2945—2012.2910 2012.2937—2013.2918 注:AREQ、TSKB站先后受到两次较大地震影响,且间隔时间不长,因此震后0~1 a、后1~2 a数据进行了顺延;ASPA站震后约1.5 a受其他地震影响,CONZ站震后临近地区地震较多,因此这两个测站震后数据未考虑;MAC1站震前约3.4 a受地震影响,因此震前4~3 a数据未考虑;MIZU站震前约2.9 a受到两次地震影响,因此震前4~3 a、前3~2 a数据未考虑. 表 3 各噪声模型未知参数个数统计
噪声模型 未知参数个数 WN 1 FN+WN、RWN+WN 2 PL+WN、FOGM+WN、FN+RWN+WN 3 FOGM+RWN+WN 4 表 4 4个测站的谱指数
测站 方向 谱指数 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ N −0.326 9 −0.528 3 −0.259 7 −0.370 1 −0.102 8 E −0.138 3 −0.413 4 −0.539 4 −0.165 1 U −0.172 7 −0.185 4 −0.414 4 ASPA N −0.429 3 −0.477 5 −0.258 2 E −0.265 1 −0.330 3 U −0.286 3 −0.107 5 MAC1 N −0.256 0 −0.445 3 −0.212 2 −0.299 6 E −0.395 1 −0.255 2 −0.368 3 U −0.338 4 −0.451 9 −0.570 2 −0.496 2 TSKB N −0.417 0 −0.298 3 −0.351 3 −0.513 6 −0.778 4 E −0.476 2 −0.473 3 −0.833 8 −1.778 5 −0.619 9 U −0.180 2 −0.671 1 −0.408 0 −1.601 7 −0.518 0 表 5 4个测站的最优噪声模型
测站 方向 最优噪声模型 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ N PL+WN FN+WN WN WN WN E WN FN+WN FN+WN WN WN U WN WN WN WN WN ASPA N PL+WN PL+WN WN E WN WN WN U PL+WN WN WN MAC1 N FN+WN FN+WN WN WN E WN PL+WN WN PL+WN U PL+WN FN+WN FN+WN FN+WN TSKB N PL+WN FN+WN FN+WN FN+WN FN+WN E FN+WN PL+WN FOGM+WN RW+WN FN+WN U WN FN+WN FN+WN FOGM+WN FN+WN 表 6 4个测站各时段分量速度场
测站 方向 速度场/(mm/a) 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ N 12.366 5 18.236 8 22.294 9 −32.300 1 3.911 3 E 13.934 6 6.083 8 72.036 0 −27.121 9 −18.963 4 U 1.104 6 11.925 9 6.292 3 −31.721 8 −18.819 3 ASPA N 33.929 6 35.733 5 34.336 6 E −62.122 4 −58.395 8 −70.915 4 U 1.307 3 0.727 2 14.618 9 MAC1 N 26.571 7 33.428 3 28.532 4 33.063 2 E −17.195 3 −8.570 8 −18.618 8 −7.934 7 U −0.466 6 −8.352 1 23.998 5 −20.962 1 TSKB N −9.754 8 −5.013 9 −8.126 4 −38.832 9 −25.859 9 E −6.117 2 11.084 5 −2.498 3 153.372 5 56.853 1 U −1.465 4 −1.594 9 −2.003 6 30.316 4 7.940 6 表 7 4个测站的周年振幅
测站 方向 周年振幅/mm 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ N 0.9572 2.723 6 4.651 1 7.153 1 3.064 8 E 7.2087 3.032 2 45.779 6 14.664 8 2.911 2 U 7.4666 10.443 5 12.036 4 11.482 8 8.317 1 ASPA N 1.6513 1.227 0 0.808 6 E 1.3665 1.828 3 1.961 7 U 1.9232 0.250 5 0.812 7 MAC1 N 0.851 4 2.117 9 0.692 1 0.825 1 E 1.056 2 2.131 8 1.002 3 0.490 5 U 2.321 7 2.116 9 11.438 3 5.677 5 TSKB N 0.0890 0.235 7 1.493 3 1.399 5 0.343 9 E 2.4666 0.580 4 2.239 6 11.228 9 2.598 1 U 5.6781 6.581 9 8.629 2 2.783 6 7.608 8 表 8 4个测站的周年相位
测站 方向 周年相位/(°) 震前4~3 a 震前3~2 a 震前1~0 a 震后0~1 a 震后1~2 a AREQ N 287.378 7 334.444 5 239.704 3 260.335 9 210.688 7 E 261.436 6 247.660 7 275.587 7 260.415 6 307.710 3 U 166.220 0 170.715 6 221.491 1 85.793 9 292.818 6 ASPA N 225.326 3 150.344 9 127.558 7 E 244.430 7 241.933 8 235.414 8 U 355.461 0 15.040 5 38.028 9 MAC1 N 226.246 8 252.039 0 286.735 7 248.051 6 E 90.982 0 244.745 2 127.684 0 149.963 9 U 117.690 8 170.335 2 284.480 2 7.808 8 TSKB N 245.710 6 322.308 4 125.543 0 332.510 3 144.096 3 E 33.449 1 121.688 3 90.432 4 193.655 2 140.580 4 U 49.418 2 36.368 3 53.846 3 322.641 9 54.378 1 -
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