台湾海峡地形地质特征及其通道工程选线

Topographic and Geological Conditions in the Taiwan Strait and Suggestion for Trans-Strait Tunnel

台湾海峡地处太平洋板块和欧亚板块碰撞带的前沿,地壳活动强烈,地震也时有发生。海峡主体属台西盆地,西界为滨海断裂带,与闽浙隆起相邻。海峡中部主要断裂,包括晋江凹陷东界主断层（F2）和九龙江凹陷东南界主断层（F3）,可能在晚上新世,甚至第四纪仍有活动。海峡南北部地形明显不同,北部地形走向为NE向,总体呈槽隆相间的格局,最大水深约90m;南部相对平坦,地形走向NS-NNW,最大水深68~70m。从拟选通道线附近的地震剖面来看,A、B、C三线附近海底均有断层,其中A、B两线F2断层明显,至少切到上新统顶界,甚至可能切入第四系;C线断层切至上新统顶界部,但主断层F3似止于上新统中部,第四纪后不再活动。台湾海峡的地震活动,南部强于北部。结合地形、地质条件、地震特征及设想隧道选线看,北线可能优于中线和南线。但由于现有资料不足以确定海底地质灾害的分布特征,建议对海峡进一步开展以工程地质、地质灾害为目的的中比例尺调查,为通道工程的科学选线提供依据。

The tectonic activity is in quite strong intensity and the earthquake happens frequently in the Taiwan Strait, as it is located at the frontier of a collision zone between Eurasian plate and Pacific plate. The main part of the strait is in the Western Taiwan Basin, with Binhai fault to the west. The main faults in the strait, including F2, eastern boundary of Jinjiang Depression and F3, southeastern boundary of Jiulongjiang Depression, may have been active in the late Pliocene, even in Quaternary. The topography in the south part of the central strait is quite different from that in the north part. The landform in the north is characterized with furrow and uplifting, with strike of NNE and the biggest depth of about 90 m, while it is much flatter in the south, with strike of NS to NNW, and the biggest depth of 68-70 m. There are faults in all 3 lines of A, B and C, based on the seismic profile near to them. The main fault F2 in line A and line B reaches the top of Pliocene at least, may even touch Quaternary, while the main fault F3 in line C reaches the mid- Pliocene and becomes non-active in Quaternary, but with some small faults to the top of Pliocene. The earthquakes are more frequent in the south than in the north. Based on the data of topography, geology and activity of earthquake, the line A should be better than the others, but more data are needed to make further validation. It is suggested that mid-scale survey of engineering geology and geo-hazard should be carried out, in order to provide more detailed information for trans-strait passage.