应用布格重力异常研究郯庐断裂构造

BOUGUER GRAVITY STUDY OF MIDDLE SECTION OF TANLU FAULT

使用布格重力资料对郯庐断裂带的中段部分（沂沭断裂带）进行了研究．结果表明，郯庐断裂带莫霍面及地壳内界面均发生错断，断裂带两侧地壳各界面起伏平缓．该结果与前人的郯庐断裂带是切穿地壳的深大断裂的认识相一致．在郯庐断裂带两侧，地壳结构明显不同，西侧沉积层较薄，平均在5km以下；东侧多数在6km以上；在断裂带中央沉积物最薄，大约为3～4km．断裂带东侧莫霍面埋深浅，大约为33～34km；西侧莫霍面埋深明显增加，达到36～38km．反映了莫霍面深度在断裂带附近整体是向西增加的．郯庐断裂带在重力场分布中则表现为一条宽度较大的线性布格重力异常梯度带．

Although the Tanlu fault is one of the most important tectonic fault zones and active earthquake belts in eastern China, little is known about its deep structure. In this study, we use the existing Bouguer gravity data to study the middle section of the Tanlu fault zone, which is also known as the Yishu fault zone. Our gravity inversion results indicate that the Moho has an abrupt offset in depth at the Tanlu fault zone and it has a relatively smooth variation away from the fault zone. The crustal structures on both sides are different from each other. Sediment is thin on the west side with an average thickness of less than 5 km, while it is as thick as 6 km on the east side. The thinnest sediment （3-4 km） is at the fault zone. Moho depth increases from 33 to 34 km on east side and from 36 to 38 km on the west side. The Tanlu fault zone shows as a wide zone of linear gradient in the Bouguer gravity anomaly.