Abstract: The north fault block in Well Huo-14 is located in deep sag of the Pemian foreland basin of Kalamaili foothill in eastern Junggar basin，in which the main body is under the overthrust nappe of Carboniferous volcanic rocks. The overlying strata of volcanic rocks with high velocity spread in wedge shape being thick in noth and thin in south, so they assume varied complex velocities that affect proper understanding of its inner structures. The forward model technique is applied to prove the existence of the north fault block and the trap shaped by the fault block. In order to describe the inner configuration accurately, a detailed interpretation has been made of its velocity spectnum, setting up average velocity fields for major strata. The abnormal velocity analysis verifies both the interpretation accu-racy and the structural configuration within the fault block.

Key words: Junggar basin, eastern Junggar, average velocity, velocity spectrum, forward, model