The mechanical properties of four faults concealed by loose Quarternary deposits in Shengli Oilfield are studied with the information of acoustic log-ging in the light of principals of mechanism geology.Various characteristics of time difference anomaly have been traced in faults of different mechanical properties

a new method for identifying them is simultaneously turned out in this paper.It is proved in the living example researched that tectonites within compresive fault belt give rise to a clearly smaller time difference of acousticwave than those of lithologically the simillar non-tectonites

that is to say

a faster acoustic velocity is transmitted by the former;on the contrary

a lar-ger time difference of acoustic wave have recorded in tectonites within tensionalfault belts

i.e.the acoustic velocity within these belts is lower.