The focal mechanisms of 239moderate and small earthquakes since 1970 in the Anhui sector of Tanlu fault zone were calculated with two methods:using the amplitude ratios of vertical P and SV waves in combination with the first motion of P,SV,and SH waves,and with 93focal mechanisms in the northern sub-sector and 146focal mechanisms in the southern sub-sector.Based on these abundant focal mechanisms,we have discussed in detail the earthquake fault types and the characteristics of the modern tectonic stressfield in the Anhui sector of Tanlu fault zone.The statistical analysis of the parameters of focal mechanism solutions shows that most moderate and small earthquakes occurring in the Anhui sector of Tanlu fault zone are of the strike-slip type,amounting to 54%of the total.Reverse faulting and normal faulting earthquakes occur less frequently,representing about 26%and 20% of the total,respectively.Azimuth and obliquity distribution of the P axis and the T axis are of obvious advantages,showing that the tectonic stress field in the Anhui sector of Tanlu fault zone and its sub-sectors is horizontally compressed in approximately the EW direction and horizontally dilated in approximately the NS direction.We further inverted the mean tectonic stress field in the Anhui sector of Tanlu fault zone and its subsectors with the force axis tensor computing method,and the results are as follows:in the Anhui sector of Tanlu fault zone,for the azimuth of maximum principal(compressive)stress axis(compression axis),σ1is 265°and its plunge is 6°;for the azimuth of the minimum principal(extensional) stress axis(tension axis),σ3is 356°and its plunge is 9°;in the northern sub-sector,for the azimuth of the maximum principal stress axis,σ1is 260°and its plunge is 4°;for the azimuth of the minimum principal stress axis,σ3is 350°and its plunge is 2°;in the southern sub-sector,for the azimuth of the maximum principal stress axis,σ1is 269°and its plunge is 8°;for the azimuth of the minimum principal stress axis,σ3is 1°and its plunge is 11°.These results indicate that the Anhui sector of Tanlu fault zone and its sub-sectors are horizontally compressed approximately in the EW direction and horizontally dilated approximately in the NS direction,which is in accord with statistical results of focal mechanism parameters.We analyzed the variation curve of the azimuth of maximum principal stress axis(σ1)versus time,which shows that the total variation trend of theσ1azimuth versus time is consistent between two sub-sectors of the Anhui sector of Tanlu fault zone,meaning both show the transition from clockwise deflection to counter-clockwise deflection in about 1998.Theσ1azimuth of the northern sub-sector experienced continued clockwise deflection from 1988to 1993,with deflected amplitude amounts to 23°,then the transition showed in 1994;a MS5.2earthquake in Cangshan,Shandong in 1995occurred after the transitions recovered,which is in accord with the variation of the trend of the P axis azimuth obtained by Zhou Cuiying([Year]),who used the method of composite focal mechanism solutions of moderate and small earthquakes.