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１９９３年５月１５日１９时，北京矿务局房山煤矿矿井下６号地震台附近，在４分多钟内相继发生３次破坏性矿震，最大一次震级为２．３级（Ｍ０＝１．５×１０１１Ｎ·ｍ）．利用理论地震图分析得到，这３次矿震都是以倾向滑动为主，与在场人员目击到的高倾角煤层中大量煤块倾泻而下的现象一致．主震及其震前一系列事件的６号台近场记录与普通记录不同，不仅有高频振动，而且还有低频振动．用弹性波理论和近年来一系列关于地震破裂成核理论结果进行分析表明：低频振动可能是亚临界扩展向前推进时激发的长周期波，它是不可恢复的形变；高频振动则是矿震事件，它是脆性破裂辐射的波场．根据Ｍ＝２．３事件记录及其震前５．４ｓ出现的前震记录中低频振动优势频率推测，主震发生时孕震断裂端部扩容区体积迅速增大．震前２０多天直到主震发生期间，震源过程主要特点如下：亚临界扩展多次出现，在此期间孕震断裂端部扩容区体积变化不大．亚临界扩展时不仅激发产生长周期波，也常同时诱发小事件的发生，亚临界扩展优势方向与主震的滑动方向基本一致．
On May 15, 1993, at 19:00, three destructive earthquakes occurred successively in the vicinity of No.6 seismic station of Fangshan Mine in Beijing Mining Bureau within 4 minutes and the maximum first magnitude was 2.3 (M0 = 1 .5 × 1011 N · m). According to the analysis of theoretical seismograms, these three earthquakes are dominated by dip-slip, consistent with the phenomenon that a large number of coal blocks are pouring down from high-angle coal seams witnessed by present personnel. The near-field records of No.6 station of the main shock and a series of events before the earthquake differ from ordinary records, not only high-frequency vibration but also low-frequency vibration. The analysis of elastic wave theory and a series of recent theoretical results on earthquake rupture shows that the low-frequency vibration may be a long-period wave excited when the subcritical expansion advances, which is an irreversible deformation. The high-frequency vibration is the ore Earthquake event, it is the wave field of brittle fracture radiation. According to the M = 2.3 event record and the predominant frequency of low-frequency vibration in the 5.4s pre-earthquake records, it is estimated that the volume of the end expansion zone at the seismogenic fault rapidly increases when the main shock occurs. During the period of more than 20 days before the earthquake, the main features of the hypocenter during the main shock are as follows: subcritical expansion occurs several times during this period, and the volume of the end expansion zone at the seismogenic fault did not change much during this period. The subcritical expansion not only stimulates the generation of long-period waves, but also often induces the occurrence of small events. The dominant direction of subcritical expansion is basically the same as the sliding direction of the main shock.