On the 1× 1 equilibrium gravity anomaly map, Jiaodong Peninsula is located in the normal anomaly area of +40× 10-5m/S2, corresponding to the tectonic uplift area on the neotectonic movement map. Modern vertical crustal deformation rate map shows that the annual crustal uplift rate of Jiaodong Peninsula is 1 ~ 2mm.
Since Cenozoic, there have been two groups of active faults in Jiaodong Peninsula, which are NNE and NNW. The Quaternary active faults are Yishu fault in northeast Shandong and Yantai-Changshan Island-Bozhong fault in northwest China, which are large in scale and active, while the Quaternary active faults in the uplift area of Jiaodong Peninsula are small in scale.
According to the nature, geomorphology and material composition of neotectonic movement, except Huangxian fault basin, most areas of Jiaodong Peninsula are relatively stable and slowly rising hilly areas, with different movement forms and activity ranges in the south, north and central parts.
The south is mainly composed of ancient metamorphic rocks and Yanshanian granite in the middle and low mountains and hills. Since Paleogene and Neogene, it has been mainly rising, and the differential activities are not obvious. Xijiaolai Plain rose steadily in Cenozoic, and suffered denudation, forming an undulating denuded plain. Since the middle and late Pleistocene, it has declined relatively, accumulating loose sediments with a thickness of 10~20m ~ 20m. Whether it is the rising range, the intensity of fault activity or the eruption of basalt, the northern region is remarkable, and it is also a region with frequent earthquakes in history.
Due to the long-term control of the east-west anticline uplift structure, the main watershed of Jiaodong Peninsula is northward, which shows that the mountain and river systems on the north and south sides are obviously asymmetrical, and also reflects the difference in rising speed between the north and south sides.
Jiaodong Peninsula has been in a state of weathering and denudation for a long time, and rising is the general trend of crustal movement in this area. But there are ups and downs in different periods, which is the characteristic of crustal movement in this area. Specific performance in the following aspects:
1. taxi plane
During the Tangshan planation, from Miocene to Miocene of Paleogene, the crustal uplift intensified, and the Luzhongyi Plain suffered cutting damage. In the early Pliocene, the crust stabilized again, forming the Tangshan planation plane. For example, Dafang Mountain in Qixia, the planation level is 15 ~ 16m higher than that of the modern riverbed, and the gravel layer accumulated by the river is covered by Paleogene basalt, showing Fangshan landform.
Planation plane in Lincheng period: the crust rose sharply at the end of Paleogene and Neogene, and the planation plane was destroyed in Tangshan period. In the early Pleistocene, the crust was stable, forming a planation plane in Lincheng period. Its altitude is100 ~130m. River facies accumulation can be seen on the planation plane, such as the yellow gravel layer left by the top of Mashan Mountain in Menlou Town, Fushan District.
2. The ups and downs of the coast
(1) The northwest sea flooded and lowered the plain coast.
It is distributed in the western part of Penglai and the Tushan area of Longkou City. Mainly for loess steep cliffs and alluvial plain banks. Such as Penglai to Luanjiakou area. The height of the steep cliff composed of loess is 20 ~ 30m.
According to the existence of ancient weathering crust under the sea surface and the characteristics of salt depression formed by seawater intrusion near the cliff, it reflects the sinking activity of the coast. However, the strip-shaped deep-sea gravel, sandy accumulation and island arc sandbar in Qimu Island, which is about 5 meters away from the coast, showed another uplift during the settlement process. According to the survey data, Huangxian-Longkou section is still a strong decline area, and its decline center is in Longkou area. The annual decline value of1953 ~197/kloc-0 reaches 700mm, which is consistent with the settlement center of Huangxian Plain.
(2) The north fault rises to the coast of bedrock harbor.
Distributed in Penglai, Zhifu and Mu Ping coastal areas. Coastline is controlled by NW-NW fault activity, forming NW-NW flat coast. The outline of the big island and the trend of the coastal ridges are mostly distributed in the northwest and northwest. For example, the topography of Zhifu Island is steep, and the coastal areas are mostly flat and steep, with a height of 50 ~ 60m, and the uplift height of marine sediments is 5 ~ 20m. There are still a series of NW-trending and NW-trending deep troughs along the coast, and the seawater is deep.
(3) the southern subsidence plain bank
Distributed in the south of Haiyang City, the coastal terrain is flat, with an altitude of 30 ~ 40m. Due to the oblique intersection of the coast and the tectonic line, the headland and bay are tortuous and changeable. Some hard rocks and scattered islands go deep into the sea to form headlands, which are generally 30-50 meters high, which is consistent with the height of the land plain.
3. Active faults
(1) ne (40 ~ 50) fault zone
The fault zone is composed of four main faults in the region, namely, Yulindian-Haiyang fault, Mu Ping-Gaojia fault and Taocun-Doushan fault from east to west, which is called Mu Ping-Jimo fault zone. These faults all show certain activity, which controls the shape and distribution of the water system in the east of Yantai, especially the Taocun-Doushan fault in the west, which has large scale, strong activity and long duration, not only affects this point.
(2) NE (15 ~ 20) fault zone.
There are fault zones in Penglai, Longkou, Qixia and Zhaoyuan to the west of Yantai, including Guguan-Majiayao fault, Su Feng-Chu Yang fault, Cunliji fault, Jushan-Biguo fault and Beigou-Linglong fault, which control the distribution and development of landforms and water systems in counties and cities to the west of Yantai. More importantly, it controls the scale of Huangxian fault basin and its eastern margin.
(3) NW fault
The NW-trending faults are scattered on land with poor continuity and small scale. According to aeromagnetic interpretation data, the northern sea area is a large fault zone, which is mainly composed of Zhifu Datun-Penglai fault and Weihai-Changdao fault. Fault activity is strong and lasts for a long time, which controls the formation and shape of coasts and islands from the perspective of geomorphology. Judging from the occurrence of earthquakes, Jiaodong earthquakes often occur on this fault zone. The recorded earthquakes of magnitude 5 ~ 6 have occurred three times in this fault zone, and the NW-trending fault is the strong active zone of earthquakes at present.
(4) Near east-west fault
The large faults near the east-west direction are mainly Wuyangquan fault in the south of Foshan city and Huangxian fault in the south of Huangcheng city. Wuyangquan fault is a large fault with strong activity. An earthquake of magnitude 5.5 occurred in 495 A.D., which is a key fault structure affecting groundwater recharge and drainage in this area. Huangxian fault is the southern margin of Huangxian fault basin, and it is a controlling fault formed in this basin.
To sum up, neotectonic activities in Jiaodong Peninsula basically inherited the characteristics of long-term rise based on the east-west anticline, but the rise on the north side was stronger than that on the south side, and the whole area was inclined to rise from northeast to southwest due to the influence of NW-trending fault activities. The multi-level nature of marine erosion platforms and planation planes in coastal areas shows that these inclinations are intermittent and tremulous. Neotectonic activity caused the peninsula to rise strongly, and the Bohai Sea and the Yellow Sea were strongly depressed or fractured, which led to strong normal fault activity of NE and NW faults in northern and coastal parts, accompanied by multi-stage basalt eruption.