Geomorphological characteristics and climate of Tumen town

Growth of all kinds of trees in Qinling Ecosphere. Timber forests include Metasequoia glyptostroboides, Pinus tabulaeformis, Pinus massoniana, Pinus armandii, Pinus taeda, Cunninghamia lanceolata, Sabina vulgaris, Populus tomentosa, Populus davidiana, Populus simonii, Populus simonii, Pterocarya stenoptera, Salix, Betula platyphylla, Ulmus pumila, Ulmus pumila, Ulmus pumila and Cinnamomum cassia.

Economic forest tree species include Cornus officinalis, walnut, persimmon, grape, chestnut, hairy chestnut, apple, peach, apricot, plum, jujube, pear, sand fruit, naphthalene, cherry, tung tree, Pistacia chinensis, pepper, lacquer tree, camellia oleifera, Quercus variabilis, mulberry, hawthorn, Xanthoceras sorbifolia, kiwi fruit, gallnut and Schisandra chinensis.

Shrubs include dustpan willow, trogopterori, jujube, coriaria, Shan Mei, Vitex negundo, Tang Di, Sabina vulgaris, Castanopsis hystrix, Rosa davurica, Lespedeza, Dioscorea bulbifera, Rhododendron, Winter jasmine, Mume, bamboo leaves pepper, Chimonanthus praecox, Begonia, Rosa rugosa, Vitex negundo, etc. According to the geological structure in Chapter 7 of Geology and Mineral Resources of Shaanxi Province, the geological structure type of Tumen Town is obviously influenced by fold structure and fault structure.

Fold structure: regionally, it belongs to the V area of the South Qinling fold belt, and the sub-area belongs to the Tangzang-Zhashui syncline belt (V 1) and the South Qinling syncline belt (V2).

1. The Tangzang-Zhashui syncline belt (V 1) is located between the Tangzang-Shangnan fault and the Fengzhen-Yang Shan fault. Its main body is composed of Middle and Upper Devonian. The Banfangzi area in the western section is a complex monocline, while the middle and eastern sections are synclines. This ore belt contains siderite and polymetallic minerals.

2. The southern Qinling syncline belt (V2) is located between the Fengzhen-Yang Shan fault, Zhuangyuan North-Madao fault and Yuehe fault (F 19), and is further divided into three belts: the northern belt (Fengxian-Zhen 'an) is a complex anticline with many secondary tight inversion folds, which is beneficial to the activation and migration of ore-forming materials, so the northern belt is important in this province. The east and west ends of the central belt (Liufengguan-Jinjiling) are synclines, and the Foping area in the middle has long been in the "bee waist" zone with the strongest north-south compression, forming a mixed rock dome. Liufengguan area is composed of five folds, with Liufengguan Group as the core, and the central zone is an important Hg-Sb metallogenic belt. The southern belt (Baishuijiang-Baihe) is composed of several anticlinorium and synclines in the Lower Paleozoic, which are fan-shaped and horseshoe-shaped in the early stage and imbricate, recumbent, overthrust and slip-off in the late stage.

Fault structures: The main structures in Tumen Town are Youfanggou-Huangtai fault (F 1 1), Tangzang-Shangnan fault (F 12) and Fengzhen-Yang Shan fault (F 13), among which Tangzang-Shangnan fault (f/kloc).

1 and Youfanggou-Huangtai fault (F 1 1) are multi-stage active fault zones composed of faults, and their occurrence changes greatly. Except for Mangling area, the dip angle is generally steep. The fault has been active in Proterozoic, and it was stretched many times from late Proterozoic to Mesozoic, which controlled the distribution of a series of fault basins. In Cretaceous, overthrust movement occurred in Mangling area, which pushed Kuanping Group over Triassic, forming Feilai peak and structural window.

2. The Tangzang-Shangnan fault (F 12) is distributed in the south of the main peak of Qinling Mountains, with a fault width of 0.5- 1 km, and the surface section is inclined to the north with an inclination angle of 60-80 degrees, which has the characteristics of multi-stage activity, controlling the distribution of fault basins, and it is still active in Cenozoic, indicating that small fault depressions appeared along the fault in the Early Tertiary and were cut by it.

3. The Fengzhen-Yang Shan fault (F 13) is distributed in the south of Yangshan and Zhashui counties. It is not obvious to the west, and the crack bandwidth is tens to hundreds of meters. The cross section is inclined to the north with an inclination of 60-80 degrees. It is a reverse fault, active in late Proterozoic, which controlled the distribution of Mesozoic fault basins, and the Cenozoic was cut by early Tertiary faults. According to the earthquake records in Shaanxi province, the thickness of the lithosphere in southern Shaanxi is about 40 ~ 46 kilometers. According to the Apparent Crustal Thickness Map of China in the Work Report on Earthquake Intensity Zoning in China published by 198 1, Shaanxi Province lies between the steep slopes of Taihang Mountain and Longmenshan Mountain, and the crustal changes in northern Shaanxi are gentle, with Guanzhong-southern Shaanxi area deepening from 35km in the east to 46km in the west, and Dali-Ankang being a twisted slope.

In recent 3000 years, the earthquakes in Shaanxi mainly concentrated in the Cenozoic fault basin of Weihe River. The earthquakes in Qinba Mountain area are scattered, with low intensity and frequency. Moderate and strong earthquakes rarely occur in northern Shaanxi. From the time series of earthquakes, they have the same characteristics in active period and quiet period, corresponding to the scale and density of active faults in the three regions.

The main faults affecting the earthquake in Tumen Town are Lanqiao-Gucheng fault zone and Shangnan fault zone in Feng Dan, Shangxian County.

1, Lanqiao-Gucheng fault zone

Also known as the iron stove fault zone. It starts in Lanchuan, Lantian, passes through Lanqiao, Mu Huguan, Tielu, Hanyuchuan, Dajing, Jingcun, Gucheng and Sanyao in Luonan County, and extends eastward into Henan. The west of Wangchuan is submerged under Cenozoic loose sediments in Weihe Basin. The fault zone is nearly east-west, with a total length of about 400 kilometers and a length of 130 kilometers in Shaanxi. The cross section inclines 50 degrees to the north.

On the mosaic map of Landsat image, the linear structural features are prominent, the color difference is obvious, the geometric shape is unique, and it has obvious branching and compound characteristics, which controls the Mesozoic and Cenozoic sediments in Luonan Basin. From the landform, it shows that the place where the big fault passes is negative topography.

This fault has obvious segmented activity characteristics, and each segment has different motion characteristics. Jingcun Village in Luonan County is located in the eastern section, and the vertical differential movement is the main movement. The Hanyuchuan section of Jingcun Village has both vertical differential movement and horizontal left-handed twisting. The Hanyuchuan-Wangchuan section is mainly left-handed twisting: the north-south river of Tieluzi-Lanqiao section turns synchronously along the fault zone without exception, indicating that both sides of the fault are left-handed twisting, and the twisting distance ranges from several hundred meters to thousands of meters.

2. Shangnan Fault in Feng Dan, Shangxian County.

From Tangyu and Lantian, it enters Feng Dan and Shangnan in Qinling, and enters Hubei in the southeast. Going northwest-southeast, Shaanxi Province is about 180 km long. The fault is composed of a series of parallel faults, which control Shangxian and Feng Dan Basin. Tertiary strata were cut and Cenozoic structural changes occurred along both sides of the fault zone. The fault cut the Quaternary strata at Kuyukou. At the intersection with the Qinling piedmont fault, Tangyu Hot Spring in Lantian is exposed, and basic and ultrabasic rocks are exposed along the fault. Geologists regard it as the dividing line to divide the inland ancient plates. There is no strong earthquake record in this fault zone.

Modern earthquake records in Shangluo area and its surrounding areas of Zhitumen Town, Shaanxi Province;

1957 65438+1October 30th 16-26-04

Epicenter: Shangxian West (33.8 degrees north latitude, 0/09.5 degrees east longitude).

Magnitude: Level 4 Epicenter Intensity: ⅴ+

Earthquake situation: In the epicenter area, the partition wall of the office building in Xiyangjia Xiequ, Shangxian County cracked, the roof tiles fell, the gables collapsed, and Yang Shan and Zhashui felt the earthquake.

Note: According to the investigation results of Lanzhou Institute of Geophysics, it is considered that the macro-epicentres are located in Wang Miao, Linchahe and Xie Yang, Dongyue, Shangxian County.

1964 June15 June 17-04-55

Epicenter: Shangnan (3: 3.3 N, 0/0/0.8 E).

Magnitude: 4

Earthquake situation: In Yunxi County, Hubei Province, people sleeping in bed felt movement, the window glass rang and the wall fell down; After the earthquake, the original crack in a room expanded by an inch; Tianhui canal collapsed in three places, about 2500 cubic meters.

Shaanxi earthquake catalogue 1973

Note: The epicenter of the earthquake in Changban Three Gorges Seismic Network was determined as Hejiajing Cave in Yunxicheng County, Hubei Province (33. 1 1'N, 1 10.39'E).

65438+April 29th 096711-17-02

Epicenter: Heyang (latitude 3510 ′, longitude110 22 ′).

Magnitude: 2.3

1August 20, 967 07-3 1-39

Epicenter: southwest of Nanzheng (32 42 ′ N, 0/06 48 ′ E).

Magnitude: 4.8; epicenter intensity: ⅵ.

Earthquake situation: tiles of houses in Nanzheng fell, and several houses in Cenzhen were knocked down by the earthquake. The river shook and many stones fell. Hanzhong, Xixiang and other places feel. As of August 23rd, 23 aftershocks were recorded, most of which were below 0.5 magnitude.

Note: Macro epicenter: (32 55 ′ n,106 44 ′ e) is in the area of Nanzheng Iron and Steel Plant and Daheba.

1967 August 21June 1 1-25-46

Epicenter: Nanzhengxi (33 00' N, 0/06 48' E).

Magnitude: 2.5

1969 12 15 06-46-23

Epicenter: Ningshan (33 24 ′ N and108 32 ′ E)

Magnitude: 2.0

1970 may1419-18-12

Epicenter: Mianxian (33 00' N, 0/06 40' E).

Magnitude: 2.0

1May 25, 970 09-25-09

Epicenter: Ankang (32 50 ′ N, 0/09 04 ′ E).

Magnitude: 2. 1

1970 12.30 06-24-26

Epicenter: Lueyang (33 21'N, 0/06 24' E).

Magnitude: 2. 1

1971March15 June 19-56-29

Epicenter: Dali (34 45' N and110' E).

Magnitude: 2.0

1971March 24th 15-45-28

Epicenter: Zhenping (3144 ′ n,10916 ′ e)

Magnitude: 2.2

1971may 31June 18-58-00

Epicenter: Zhenping (3148 ′ n,10912 ′ e)

Magnitude: 3. 1

1August 30, 972 22-58-26

Epicenter: Fengxiang (34 37' N, 0/07/0/6' E).

Magnitude: 2.4

Earthquake situation: The sensing range includes Yangguanguan, Wenjiapo, Nanzhai, Huangli and Liulin towns in Fengxiang County. In the induction area, people usually hear the sound first, and people feel shaking, the window paper rings, the electric light shakes, the kiln roof falls off, and some people feel dizzy; Wen Jiabo's house has cracks.

197265438+1October 12 28- 18-09

Epicenter: Longxian (34 51'N, 0/06 43' E).

Magnitude: 2.2

1973 February 14 28-58

Epicenter: Longxian (34 39 ′ N, 0/06 57 ′ E).

Magnitude: 3.0 epicenter intensity: Ⅳ+

Earthquake: The sensing range is from Chicheng, Chongxin County, Gansu Province in the north, Liu Da Village in the south, Houjia Temple in the west and Huoshaozhai in the east. The isoseismic line is oval, and its long axis is north-south-southwest. At first, you hear the noise of the ground, such as trucks passing by and doors and windows ringing. Then you feel the ground shaking, the ceiling falling, hanging objects shaking, bottles shaking and small objects shifting. Most people wake up from their dreams, and some people.

February 1973 survey report of felt earthquake in Longxian County, Shaanxi Province by Shaanxi Earthquake Team.

1973 August1012-40-10

Epicenter: Hancheng (35 24' N,11917' E).

Magnitude: 2.7

1August 20, 973 20-07-22

Epicenter: Hancheng (35 20 ′ N,110 23 ′ E)

Magnitude: 2.2

1973165438+1October 22nd 0 1-56-03

Epicenter: Shiquan (33 07 ′ N, 0/08 20 ′ E).

Magnitude: 2.3

197365438+February 2 1 1-09-29

Epicenter: Dali (35 degrees 00 minutes north latitude, 1 10 degrees 06 minutes east longitude)

Magnitude: 2.4

1April 27, 974 15-08-46

Epicenter: Hancheng (35 24' N,110 31'E)

Magnitude: 2.2

1974 May 31June 16-23-23

Epicenter: Longxian (34 55 ′ N, 0/06 57 ′ E/KLOC).

Magnitude: 3.7

Earthquake: the whole county of Longxian has a feeling.

1974 July1June 1 1-35- 18

Epicenter: Xunyang (33 08 ′ N, E109 02 ′)

Magnitude: 2.2

1974 July 21June 13-26-52

Epicenter: Heyang (latitude 35 21',longitude110 21')

Magnitude: 2.0

1974 12 13 20- 19- 1 1

Epicenter: Ningshan (33 24' N, 0/08/0/4' E).

Magnitude: 2.3

1976 65438+ 10/0/309-21-26

Epicenter: Shiquan (latitude 33 04 ′, longitude108 09 ′)

Magnitude: 2.6

1977 June

Epicenter: Zhen 'an (33 27 ′ N, E10911′)

Magnitude: 2.2

1977 August

Epicenter: Gao Lan (32 N19 ′, E10818 ′).

Magnitude: 2.0

1August 23, 977 04-05-32

The epicenter; The northern suburb of Xi 'an (34 25 ′ N, 0/08 53 ′ E/KLOC).

Magnitude: 2.9

Earthquake: Xi 'an, Gaoling, Xianyang, Jingyang and Lintong have feelings.

1September 5, 977 02-24-27

Epicenter: North suburb of Xi 'an (34 24 ′ N, East longitude108 59 ′)

Magnitude: 2.2

Earthquake situation: Xi' an has a feeling.

1978 February1108-11-21

Epicenter: Shiquan Changshui (32 48 ′ N, E108 08 ′)

Magnitude: 4.2, epicenter intensity: ⅴ.

Earthquake situation: The polar earthquake zone is oval, distributed in Chazhen, Xixiang County, Hanyang and Vortex, Yuancheng, Shuang 'an and Shiquan Changshui, Ziyang County. The long axis direction is northwest, and most people can feel it, such as muffled thunder and shooting. People who escape from the house occasionally wake up. Doors and windows, roof trusses and ceilings shake off soil, and tiles occasionally fall on houses and rammed earth walls.

Earthquake precursor phenomenon: the day before the earthquake, cows were barking, pheasants were flying in surprise, and cows were not allowed to enter the circle at night. A well in Seoul Middle School in Ziyang County is 1 1 m deep. The water level began to decline in the winter before the earthquake 1977, and almost dried up on February 5 1978, and the water level rose after the earthquake.

Investigation report of Shiquan earthquake with Ms 4.2 by Seismological Bureau of Shaanxi Province, mimeographed.

1978 March11October 23rd-19-04

Epicenter: Lintong (34 35' N, 0/09/0/3' E).

Magnitude: 2.3

1March 27, 978 09-50-05

Epicenter: Lintong (latitude 34 33', longitude 109 10')

Magnitude: 2. 1

1June 27, 978 08-52- 10

Epicenter: Longxian County (34 59 ′ N and107 04 ′ E)

Magnitude: 2.0

1978165438+18 October 07-39-57

Epicenter: Shiquan (latitude 32 59 ′, longitude108 06 ′)

Magnitude: 2.0

1980 1.7 03- 14-08

Epicenter: Feng Dan (33 degrees 40 minutes north latitude and1/kloc-0 degrees 26 minutes east longitude).

Magnitude: 2.3

1981April 20th17-19-11

Epicenter: Shangnan (3318 ′ N, 0/10 52 ′ E).

Magnitude: 2. 1

1981September 19 08-55-55

Epicenter: Mianxian (33 01'N, 0/06 43' E).

Magnitude: 2.0

198 1 year1February 1 1 day 12-50-80

Epicenter: Mianxian (33 03' N, 0/06 32' E/KLOC).

Magnitude: 2.0

1982 August11June 18-42-57

Epicenter: Yangshan Banquet Horse (latitude 3315 ′, longitude110 21′)

Magnitude: 4.5 epicenter intensity: ⅵ+

Earthquake situation: the ⅵ degree area is oval, and the long axis is NE direction. People in the epicenter felt thrown up, the ground rumbled, and pedestrians felt the ground roll like waves. Half an hour after the earthquake, white smoke was still blowing on the Wuli River.

The steep limestone mountain on the bank of Wulihe River is cracked, with a total of 270,000 cubic meters of collapsed deposits, and the largest collapsed block can reach 5,000 cubic meters. The collapsed material blocked the river, cracked the river bed, and leaked the river water within hundreds of meters. In Huangjiagou, about 500 meters northwest of the collapse site, many houses were damaged, eaves purlins fell off, walls collapsed and cracked, roof tiles fell off, walls separated from house frames, and roof chimneys collapsed.

There are few aftershocks after the main earthquake.

Seismological Bureau of Shaanxi Province "1982 Yang Shan Earthquake with Ms 4.5"

1982 April 22-37-47

Epicenter: Yang Shan Yu Zhen

Magnitude: 2.7

198410/October 26th 14-35-4 1

Epicenter: Baihe (33 07' N, 0/09 50' E).

Magnitude: 2.2

1985 September 14 June 12-08-03

Epicenter: Xunyang (33 04 ′ N, 0/09 46 ′ E/KLOC).

Magnitude: 2.9

There is a sense of earthquake in Manchuan area of Shanyang County.

65438+June 22nd 0986 15-57-54

Epicenter: Xunyang (33 05 ′ N, 0/09 27 ′ E).

Magnitude: 2.2