The gas anomalies in the CCSD borehole associated with two distant strong earthquakes: the 2001 West Pass of Kunlun Mountains earthquake (Ms 8.1) and the 2004 Sumatra-Andeman earthquake(Mw 9.3)
中国大陆科学钻探主孔流体地球化学异常与远强震的关系

Based on the research of the fluid compositions in the mud of Chinese Continental Scientific Drilling Hole,short-term anomalies before and after two distant big earthquakes,the Nov.14,2001 West Pass of Kunlun Mountains Earthquake with M_s 8.1 and the Dec.26,2004 Sumatra-Andeman earthquake with M_s 8.7 (M_w 9.3),were recognized.The values of the concentration of He and the N_2/O_2,He/Ar,N_2/Ar ratios had changed significantly 2-7 days before the two distant earthquakes occurred.The abnormalities of the two earthquakes changed in the similar trends.The abnormalities of the concentration of He and the ratios of N_2/O_2,He/Ar and N_2/Ar show obviously negative,however,the ratio of Ar/O_2 changed reversely.The gas anomalies before and after the two distant earthquakes show very different from those of small earthquakes near the CCSD horehole.The evidence suggests that the concentration and ratio of compositions in the fluid of CCSD might be sensitive to the occurrences of distant strong earthquake.It might be the transmitting of long period wave during the event which triggered the changes of the concentration and ratio of fluid compositions. On the other hand,the anomalies might reflect the focal precursors and field precursors produced by a regional or deep tectonic activity.