2021年玛多M_(S)7.4地震的PI热点特征回溯性预测研究

Retrospective Study on the Forecast of the 2021 Maduo M_(S)7.4 Earthquake by PI Method

应用图像信息(PI)方法研究2021年玛多M_(S)7.4地震前后的热点特征变化。以8 a预测窗长、0.8°×0.8°网格尺度为主要参数,获取2009—2028年逐年滑动的预测窗热点分布图像。结果显示:(1)在2009—2020年的5个连续回溯性预测窗口中,玛多地震的震中所在网格及其摩尔邻近网格持续存在密集热点,对发震地点指示作用较强。(2) 2014—2028年,多数预测窗口内玛多地震震中或摩尔邻近网格出现过PI热点;在最后3个连续预测窗口内(2019—2026年、2020—2027年、2021—2028年),震中附近出现密集深色热点且呈逐渐收缩的趋势,对发震紧迫性具有一定的指示意义。(3)综合2009年以来的热点演化图像可知,巴颜喀拉地块、柴达木地块、祁连地块和羌塘地块内都出现过热点,出现在巴颜喀拉地块与柴达木地块交界玛多县附近的热点频次高、颜色深、覆盖面较大,表明青藏块体内部巴颜喀拉地块中北缘地震活动性较强、相对发震风险较高。

In this paper, the Pattern Informatics(PI)method was applied to the retrospective study on the forecast of the 2021 Maduo M_(S)7.4 earthquake.The local area(30.0°N-40.0°N,94.0°E-106.0°E)of Qinghai-Tibet tectonic block was chosen as the study region.With parameters of the 8-year-long forecasting window and the 0.8°× 0.8°-sized grid, successive forecasting hotspot diagrams were obtained in the period from 2009 to 2028.The results showed that:(1)In five successive forecasting windows covering the period from 2009 to 2020,continuous dense hotspots appeared in the grid in which the Maduo epicenter located and in its neighboring Moore grids.These hotspots strongly indicated the location of the Maduo earthquake.(2)In the period from 2014 to 2028,PI hotspots appeared in the grid in which the Maduo epicenter located or in its neighboring Moore grids in most forecasting windows.In the three continuous forecasting windows after 2018(2019-2026,2020-2027 and 2021-2028),dark hotspots appeared near the epicenter of the Maduo M_(S)7.4 earthquake and showed a gradual tendency of contraction, which indicated the impending occurrence of the Maduo M_(S)7.4 earthquake.(3)According to the continuous hotspot diagrams since 2009,hotspots appeared in the Bayankala block, the Qaidam block, the Qilian block and the Qiangtang block.Relatively, hotspots appearing at the junction of the Bayankala block and the Qaidam block near Maduo county had higher frequency, darker color, larger coverage.The results indicates that the middle part of the northern margin of the Bayankala block in the Qinghai-Tibet tectonic block has stronger seismicity and higher potential earthquake risk.