地震研究

2014年于田M_S7.3地震的疑似障碍体效应^*

刘双庆¹,陈向军²,王熠熙¹,王俊菲³

(1.天津市地震局,天津 300201; 2.新疆维吾尔族自治区地震局,新疆乌鲁木齐 830011; 3.江苏省地震局,江苏南京 210014)

A Speculative Barrier Effect of Yutian M_S7.3 Earthquake in 2014

LIU Shuangqing¹, CHEN Xiangjun², WANG Yixi¹, WANG Junfei³

(1.Earthquake Administration of Tianjin Municipality, Tianjin 300201, China)(2. Earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi 830011, Xinjiang, China)(3. Earthquake Administration of Jiangsu Province, Nanjing 210014, Jiangsu, China)

Keywords： Hetian array; Pn phase; rupture spread; barrier

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参考文献

利用新疆和田台阵首波Pn段前4 s的高频波动形态,分析了2014年于田M_S7.3主震破裂初期几个疑似破裂点的相对位置,给出两种可能的初始破裂点运动学扩展模型。并利用震中距约58 km的于田台站数据进一步对该模型进行阐述。分析结果推测:此次于田大地震,其起始破裂点开始于一个水平各向异性较强的点位,在之后的3 s内破裂过程向各向异性相对较弱的区域发展,且破裂矢量略向南扩展。

Depending on the high frequency waveform in forepart 4 s of Pn, which was recorded by Xinjiang Hetian array, we analyzed the relative position of several speculative forepart rupture in the initial period of Yutian M_S7.3 main shock in 2014, and introduced two concessional rupture kinematics models to explain the observation phenomena. Aim to deeply study the feasibility and veracity of these two models, we also used seismic wave recorded by Yutian Station. The following conclusion was given that the first rupture of the Yutian earthquake would start at an intensively horizontal anisotropic position, and then transmitted into much less anisotropic area in the succedent 3 s. The direction of the short rupture process showed a slight southern trend.

引言
1 和田台阵入射线方位角分析
2 台阵Pn段的高频时间不同步性分析
3 结论与讨论

图1 于田MS7.3地震的震中、震源机制、和田台阵、于田台站分布<br/>Fig.1 Distribution of epicenters, focal mechanisms of Yutian MS7.3 earthquake, and Hetian array and Yutian Station

图1 于田MS7.3地震的震中、震源机制、和田台阵、于田台站分布
Fig.1 Distribution of epicenters, focal mechanisms of Yutian MS7.3 earthquake, and Hetian array and Yutian Station

图2 和田台阵扫描不同方位角时差所获取的震中—台站方位角<br/>(a)台阵子台分布及互相关获取的相对走时差;(b)不同方位角上计算的走时与互相关时差的绝对差值<br/>Fig.2 The epicenter-azimuth estimated by scanning the travel-time differences of different azimuth in Hetian array(a)distribution of sub-stations and their relative travel-time residuals obtained by cross-correlation; (b)absolute time difference between theoretic and cross-correlation in different azimuth

图2 和田台阵扫描不同方位角时差所获取的震中—台站方位角
(a)台阵子台分布及互相关获取的相对走时差;(b)不同方位角上计算的走时与互相关时差的绝对差值
Fig.2 The epicenter-azimuth estimated by scanning the travel-time differences of different azimuth in Hetian array(a)distribution of sub-stations and their relative travel-time residuals obtained by cross-correlation; (b)absolute time difference between theoretic and cross-correlation in different azimuth

图3 和田台阵9个子台Pn段的波形展示<br/>Fig.3 The display of waveforms of head wave Pn recorded by 9 sub-stations of Hetian array

图3 和田台阵9个子台Pn段的波形展示
Fig.3 The display of waveforms of head wave Pn recorded by 9 sub-stations of Hetian array

图4 和田台阵相对于6号子台的走时差分析<br/>(a)不同子台4个时刻点各到时与6号子台的差值;(b)后1时刻各子台时间差与第1时刻<br/>各子台的时间差之再差值(仍以6号子台做基准)<br/>Fig.4 Analysis of travel time difference in Hetian array that compared with the No.6 sub-station(a)traval time difference between sub-stations and the No.6 sub-station at four time-spots; (b)time difference of every sub-station by second-dedueted on Fig.4a(tabe No.6 sub-station as the reference)

图4 和田台阵相对于6号子台的走时差分析
(a)不同子台4个时刻点各到时与6号子台的差值;(b)后1时刻各子台时间差与第1时刻
各子台的时间差之再差值(仍以6号子台做基准)
Fig.4 Analysis of travel time difference in Hetian array that compared with the No.6 sub-station(a)traval time difference between sub-stations and the No.6 sub-station at four time-spots; (b)time difference of every sub-station by second-dedueted on Fig.4a(tabe No.6 sub-station as the reference)

图5 3种不同震源破裂点处的介质模型垂向剖面
Fig.5 Sketch map of vertical profile of models for anisotropic medium at the location of three kinds of focal rupture

图6 相似震中距的两台站记录不同震级的地震波形特征对比(图c、g取Pg前0.3 s对齐)(a～d)于田台站记录的于田MS7.3地震;(e～h)南山村台站记录的宝坻MS4.0地震<br/>Fig.6 Earthquake waveform comparison of different magnitude recorded by two stations with close epicenter-station distances(the waveform in fig.c and fig.d align by the first 0.3 s of Pg)(a～d)Yutian MS7.3 earthquake recorded by YUT Station;(e～h)Baodi MS4.0 earthquake recorded by NSC Station

图6 相似震中距的两台站记录不同震级的地震波形特征对比(图c、g取Pg前0.3 s对齐)(a～d)于田台站记录的于田MS7.3地震;(e～h)南山村台站记录的宝坻MS4.0地震
Fig.6 Earthquake waveform comparison of different magnitude recorded by two stations with close epicenter-station distances(the waveform in fig.c and fig.d align by the first 0.3 s of Pg)(a～d)Yutian MS7.3 earthquake recorded by YUT Station;(e～h)Baodi MS4.0 earthquake recorded by NSC Station

图7 沿走向破裂10 km后各子台相对走时差分析<br/>(a)沿震中P1向西南破裂到P2,或向东北破裂到P3的放大模型; <br/>(b)向西南或向东北破裂产生的子台相对时差<br/>Fig.7 Analysis on the relative travel-time residuals among sub-stations after ruptured 10 km along strike(a)enlarge rupture model from epicenter P1 to P2 or P3, respectively along southwest or northeast direction; (b)relative time residuals of sub-stations as rupturing along southwest or northeast direction

图7 沿走向破裂10 km后各子台相对走时差分析
(a)沿震中P1向西南破裂到P2,或向东北破裂到P3的放大模型;
(b)向西南或向东北破裂产生的子台相对时差
Fig.7 Analysis on the relative travel-time residuals among sub-stations after ruptured 10 km along strike(a)enlarge rupture model from epicenter P1 to P2 or P3, respectively along southwest or northeast direction; (b)relative time residuals of sub-stations as rupturing along southwest or northeast direction