Abstract: Apparent stresses and differential apparent stress of the Nov.29,1999 Xiuyan . earthquake sequence was recalculated by using two different geometric spreading models such as spherical and three distinct sections geometric spreading model,using the wave form data from July 1999 to May 2000 by the Shenyang Digital Seismic Station Network, Liaoning province. We analyzed and compared the temporal variations of single-station and multi-station averages of apparent st resses of two different geometric spreading models and the apparent stresses of the same earthquake. Our results show that, (1) For the same earthquake, the apparent stress calculated by using spherical geomtric spreading model is bigger than that of using three distinct sections geometric spreading model, the apparent stress considering energy compensation is more bigger than that of no energy compensa-tion; (2) The characteristic of apparent stresses of the Xiuyan sequence is that low appar ent stress level in a long time before the main shock, rising a couple of days before the main shock, high apparent stress level during the time after the main shock and before the biggest aftershock, reducing and returning to the low apparent stress level after the big-gest aftershock; (3) Using spherical or three distinct sections geometric spreading model, considering energy compensation or not, using single station apparent stress or multi-star tion average apparent stress, there is almost no difference on the judgment of seismic tend-ency; (4) Using spherical or three distinct sections geometric spreading model, differential stress shows a rapidly rising process in a short time before the M_s5.4 main shock and the biggest M_s5.1 aftershock.

Key words: Apparent stress, Geometric spreading model, Energy compensation, The Nov.29, 1999 Xiuyan sequence