云南小江断裂带中段的微震活动性――PALM自动检测方法在密集台阵中的应用

利用北京大学2016—2019年在小江断裂带中段布设的20个宽频带流动测震台和云南测震台网的3个固定台站的波形数据, 对北京大学开发的地震自动检测与定位程序PALM的有效性进行测试, 完成研究区的微震检测和精定位。共检测出4355个地震事件, 是云南台网地震目录中的4.6倍, 最小完备震级Mc值从M_L1.3降至M_L 0.8, 说明PALM技术可以在高密度地震台阵中有效且准确地检测微地震并进行定位, 提高台阵地震资料分析的智能化水平和微震检测能力。基于获取的包含丰富微震事件的目录, 研究结果勾画出小江断裂带中段地震活动的最新空间分布特性, 显示小江断裂带在主断层之外发育大量次级断层, 走向大致为东北东?西南西。研究区南端可能存在一条未曾发现的隐伏断层, 宜良县柴石滩水库周边检测出密集的微震活动。

Microseismicity in Central Xiaojiang Fault Zone,Yunnan:Application of PALM on Dense Seismic Network

Based on the continuous waveforms (2016?2019) of 20 portable broadband seismic stations and three local stations deployed in the middle section of Xiaojiang fault (XJF), the effectiveness of PALM (phase picking, association, location, and matched filter) was tested as an integrated event detection system, to perform automatic earthquake detection, positioning and matched-filter studies. A total of 4355 earthquakes were detected. In comparison with the catalog of the regional network, the number of events was augmented by 4.6 times, and the minimum magnitude of completeness (Mc) is reduced from M_L 1.3 to M_L 0.8. It shows that PALM technology can effectively and accurately detect and locate micro-earthquakes using dense seismic arrays, and improve the automation level and microseismic detection from continuous waveforms. Based on the obtained catalog rich in microseismic events, the result shows that the latest spatial distribution characteristics of seismic activity in the middle section of XJF zone. It shows that a large number of secondary faults are developed in XJF fault zone outside the main fault, and the trend along ENE-WSW, which reveals a possible hidden fault at the southern end of the study area, and detects dense clusters around the Chai Shi Tan Reservoir in Yiliang County Microearthquake activity.