土耳其地震序列的近断层脉冲型地震动识别与特征分析

Identification and characterization of pulse-like ground motion in the Turkey earthquake sequence

2023年2月土耳其东安纳托利亚断裂带连续发生多次6级以上强震,为揭示此次强震序列中的近断层地震动特征,选取土耳其M_(w)7.8、M_(w)7.5、M_(w)6.7和M_(w)6.3的四次地震中的781组强震记录,基于能量法识别获得45条水平向脉冲型地震动记录和17条竖向脉冲型地震动记录,其中水平向75%的脉冲型地震动记录来自于M_(w)7.8地震。通过分析识别的速度脉冲记录表明,存在相同台站竖向为脉冲型地震动而水平向为非脉冲型地震动的现象;土耳其地震序列的速度脉冲具有周期短、幅值大的显著特点,其中8002台站记录的最大脉冲周期达到7.57 s、3138台站记录的最大脉冲幅值达到231.30 cm/s。通过分析矩震级对脉冲周期的影响和脉冲幅值随矩震级和断层距的变化规律表明,水平向速度脉冲周期随矩震级呈对数线性增大,在相同矩震级情况下脉冲周期明显小于已有模型的预测值;脉冲幅值随断层距的增加存在明显衰减的趋势,当断层距小于25 km时,脉冲幅值普遍高于已有预测模型。研究结果表明土耳其地震序列产生了大量的近断层脉冲型地震动,识别结果丰富了全球近断层脉冲型地震动数据库,揭示的特征可为震害分析和脉冲模型建立提供参考。

In February 2023,Turkey’s East Anatolia Fracture zone had multiple strong earthquakes of M≥6.Here,to reveal characteristics of near fault ground motions in this strong earthquake sequence,781 sets of strong ground motion records of the 4 earthquakes of M_(w)7.8,M_(w)7.5,M_(w)6.7 and M_(w)6.3 in Turkey were selected,and 45 horizontal pulse-like ground motion records and 17 vertical pulse-like ground motion records were obtained based on identification with the energy method,in which 75%of horizontal pulse-like ground motions records came from M_(w)7.8 earthquake.Velocity pulse records identified through analysis showed that there are phenomena of vertical direction ground motions being pulse type while horizontal direction ground motions being non-pulse-like at the same station;velocity pulses of Turkey earthquake sequence have features of short period and large amplitude,the maximum pulse period recorded at station 8002 reaches 7.57 s,and the maximum pulse amplitude recorded at station 3138 reaches 231.30 cm/s;through analyzing effects of moment magnitude scale on pulse period and variation of pulse amplitude with changes of moment magnitude scale and fault distance,horizontal velocity pulse period increases logarithmically linearly with increase in moment magnitude scale,and pulse period is obviously smaller than the predicted value of existing models under the same moment magnitude scale,pulse amplitudes have an obvious attenuation trend with increase in fault distance,when fault distance is less than 25 km,pulse amplitudes are generally higher than those of existing prediction models;the study results reveal Turkey earthquake sequence producing a large number of near fault pulse-like ground motions;the recognition results enrich the global near fault pulse-like ground motion database,the revealed features can provide a reference for earthquake damage analysis and establishing pulse model.