Seismic tomography of Yunnan region using short-period surface wave phase velocity

利用云南数字地震台网23个台站记录的短周期(1～18s)面波资料，用双台窄带通滤波互相关方法，测定了在209条路径上的基阶瑞利波相速度频散曲线，并通过层析成像反演得到各周期的相速度分布图象．给出了沿24°N，25°N，26°N及27°N和100．5°E的相速度频散剖面图．结果表明：云南地区的相速度分布图象具有强烈的横向变化，短周期段的相速度分布与沉积层厚度密切相关，中甸、丽江东部区域在约25km深度存在着明显的低速层，而畹町、云县、思茅一带在该深度范围是一明显的大面积高速区域．小江断裂与红河断裂围成的川滇菱形块体南段为低相速度区域．云南地区强震震中位置主要分布在相速度高速与低速过渡的区域．

Study on the Recent Tectonic Stress Field in the Yunnan Region

In this paper, using focal mechanism solutions of moderate-strong earthquakes in Yunnan and its adjacent areas, and based on the statistical analysis of the parameters of focal mechanism solutions, we discussed in detail the earthquake fault types and the characteristics of the modern tectonic stress field in the Yunnan region. The results show that most moderate-strong earthquakes occurring in the Yunnan region are of the strike-slip type, amounting to 80% of the total. Normal faulting and normal with strike-slip and reverse and reverse with strike-slip earthquakes is almost equivalent in proportion, about 8% each. The tectonic stress field of the Yunnan region is near-horizontal, and the dips of earthquake fault planes are large. There are three main dynamic sources acting on the Yunnan region: one is the NE, NNE and NNW-directed acting force from Myanmar, Laos and Vietnam; the second is the SE-SSE directed force from the Sichuan and Sichuan-Yunnan rhombus block and the third is the NW-NNW directed force from the South China block. These three acting forces have controlled the faulting behavior of the main faults and the characteristics of strong earthquake activity of Yunnan and its adjacent regions.

Construction Techniques of Wooden Dwelling Column Frame in Tibetan Regions of Yunnan Province, China

Column frame of folk dwellings with slope roof in Tibetan regions of Yunnan Province was studied. Through field investigation and surveying, column frame timber, main components and construction techniques were introduced. The research showed that column frame of slope-roof dwelling in Tibetan regions of Yunnan is a regional construction technique using timber as the major materials, tenon-and-mortise work as the major connection, characterized by excellent structural expandability, and shock resistance, but it has no quantitative technical support. Scientific and systemic study is needed to improve safeness and livability of local dwellings.

Regional stress field in Yunnan revealed by the focal mechanisms of moderate and small earthquakes

We determined focal mechanism solutions of 627 earthquakes of magnitude M ≥ 3.0 in Yunnan from January 2008 to May 2018 by using broadband waveforms recorded by 287 permanent and temporary regional stations. The results clearly revealed predominantly strike-slip faulting characteristics for earthquakes in Yunnan, with focal depths concentrated in the top 10 km of the crust. The earthquake mechanisms obtained were combined with the global centroid moment tensor solutions of 80 additional earthquakes from 1976 to 2016 to invert for the regional variations of stress field orientation by using a damped regional-scale stress inversion scheme.Results of the stress field inversion confirmed that the Yunnan region is under a strike–slip stress regime, with both maximum and minimum stress axes being nearly horizontal. The maximum compressional axes are primarily oriented in a northwest-southeast direction, and they experience a clockwise rotation from north to south, whereas the maximum extensional axes are oriented largely northeast-southwest. The maximum compressional axes are in line with the global positioning system–inferred horizontal velocity field and the southeastward escape of the Sichuan–Yunnan Rhombic Block, whereas the maximum extensional axes are consistent with anisotropy derived from SKS splitting. Against the strike–slip background, normal faulting stress regimes can be seen in the Tengchong volcanic area as well as in other areas with complex crisscrossing fault zones.

Deep medium environment of strong earthquakes occurrence in Yunnan region

The deep structure background of earth medium for strong earthquakes ccurrence in Yunnan area is discussed inthis paper, by using the results on the study of the velocity structure, elect fieal conductivity stricture, geothermalstructure in the crust and upper mantle in Yunnan area. The results show that the occurrence of strong earthquakes in Yunnan region is obviously related to the deep medium and tectonic environment such as the existenceof the high velocity zone in the upper crust, the low velocity zone or high electrical conductivity layer in themiddle crust, local uplift in the upper mantle, high geothermal activity and deep and large fault, etc. The large earthquakes could not take place at anywhere, they often occur at some regions which have a certainbackground in the deep medium structure. The activity of the earthquakes with magnitude of 5 or less is quite random,the occurrence of them have not the obvious background of the deep medium strUcture.

The impact of land use on soil properties in a karst agricultural region of Southwest China: a case study of Xiaojiang watershed, Yunnan

Supported by RS and GIS, the land use change from 1982 to 2003 were analyzed and the impacts of land use changes on pH value, organic matter, total N, total P, total K, available N, available P, and available K in soil of Xiaojiang watershed, a typical karst agricultural region of Yunnan Province, Southwest China were assessed. The following aspects are concluded. （1） The total land use converted during the past 20 years in Xiaojiang watershed covers an area of 610.12 km^2, of which 134.29 km^2 of forestland was converted into cultivated land, and 210 km^2 of.unused land was converted into cultivated land. （2） The rapid growth of population and the economic development were the main driving forces of land use change. （3） With the change in land use, the soil properties have been changed significantly. The pH, organic matter, total N, total P, total K, available N, available P and available K in soil in 1982 were 6.3, 38.02 g·kg^-1, 1.86 g·kg^-1, 1.63 g·kg^-1, 10.94 g·kg^-1, 114.42 g·kg^-1, 11.65 mg·kg^-1 and 64.69 mg·kg^-1g, respectively; and those in 2003 were 6.73, 25.26 g·kg^-1, 1.41 g·kg^-1, 0.99 g·kg^-1, 12.6 g·kg^-1, 113.43 mg·kg^-1, 11.11 mg·kg^-1 and 151.59 mg·kg^-1, respectively. Pared samples t-test of the tested indices of soil properties indicate that those indices have changed significantly during the last 20 years. But the soil properties changed differently, due to the differences in land use change. （4） Also, with the change in land use and management measures of soil, the modifications in soil properties which developed from carbonate rocks were more sensitive than those in the soil developed from sandstone.

Seismic tomography of Yunnan region using short-period surface wave phase velocity

The data of short-period (1~18 s) surface waves recorded by 23 stations belonging to the digital seismic network of Yunnan Province of China are used in this paper. From these data, the dispersion curves of phase velocities of the fundamental mode Rayleigh wave along 209 paths are determined by using the two-station narrowband filtering cross-correlation method. Adopting tomography method, the distribution maps of phase velocities at various peri-ods in Yunnan region are inverted. The maps of phase velocities on profiles along 24N, 25N, 26N, 27N and 100.5E and the distribution maps of phase velocities at 3 periods in the study region are given. The results show that the phase velocity distribution in Yunnan region has strong variations in horizontal direction, and the phase velocity distribution in short-period range is closely related to the thickness of sedimentary layers in the shallow crust. The phase velocity in southern part of the Sichuan-Yunnan rhombic block encircled by the Honghe fault and Xiaojiang fault is obviously lower than that in surrounding areas. The epicentral locations of strong earthquakes in Yunnan region are mainly distributed in transitional zones between low and high phase velocities.

Notes on the key role of stenochoric endemic plants in the floristic regionalization of Yunnan

With the accumulation and accessibility of information about plant species,it is time to re-evaluate and further divide a global biodiversity hotspot region,Yunnan,located in southwestern China.In this study,we combined data on the distribution of 1010 stenochoric endemic seed plants,vegetation constitution,geological history and climate change,and used these to propose a new system of floristic regions.We identified 11 distinct floristic subregions and 84 floristic provinces within Yunnan.Our work confirmed some views emphasized by Wu Zhengyi that the stenochoric endemic species play a key role in defining floristic provinces;that stenochoric endemic plants with long collection and publication histories are more valuable;that greater attention should be paid to woody plants;and that for Yunnan,a border region,some trans-border distributed elements should be treated cautiously.

Q value of anelastic S-wave attenuation in Yunnan region

The study of seismic attenuation property is a major subject in seismology. Seismic waves recorded by seismic stations （seismographs） contain source effect, seismic wave propagation effect, site response of seismic stations and instrumental response. The path effect of seismic wave propagation, site response of seismic stations and instrumental response must be taken out in the study of source property with seismic data. The path effect of seismic wave propagation （seismic attenuation） involves an important influential factor, the anelastic attenuation of medium, which is measured with quality factor Q, apart from geometric attenuation with the distance. As a basic physical parameter of the Earth medium, Q value is essential for quantitative study of earthquakes and source property （e.g. determination of source parameters）, which is widely used in earthquake source physics and engineering seismology.

International Comparison and Implications of Agricultural Development in Foreign Low Latitude Plateau Regions for Yunnan Province

Climatic characteristics of foreign low latitude plateau regions are firstly introduced.Then,experience and lessons of major foreign low latitude plateau countries in developing modern agriculture are analyzed,including Indian three agricultural revolutions and agricultural informationization development,application of agricultural biotechnology in Brazil,trade liberalization and economic de-agriculture of Mexico,and Argentina,Saudi Arabia and South Africa attaching great importance to developing modern agriculture relying on science and technology and paying close attention to resource conservation and environmental protection.Combining natural and social resource characteristics of Yunnan plateau agriculture,pertinent implications and recommendations for modern agricultural development in Yunnan are put forward.Specifically,these include strengthening agricultural sci-tech research and development,and extension and application;transforming agricultural development model;enhancing agricultural resource conservation and environmental protection;accelerating developing mountain organic ecological agriculture and autumn agriculture;reinforcing urban and rural integration to develop plateau characteristic agriculture on the basis of local actual conditions.

Frequency-dependent attenuation of P and S waves in Yunnan region

We analyzed digital seismogram data of 5668 earthquakes that occurred in Yunnan region between July of 1999 and December of 2003. Among the 22 seismic stations, six ones, namely Baoshan, Yongsheng, Lijiang, Heqing, Yimen, and Luquan, were selected and their attenuations of P and S waves were measured by using the extended coda-normalization method. The six stations were classified into three regions according to their location, that is, Baoshan area, Yongsheng-Lijiang-Heqing (YLH) area and Luquan-Yimen (LY) area. The values of QS-1 and QP-1 are expressed as QS-1=0.00867 f-0.86, QP-1=0.01155 f-0.93, QS-1=0.01824 f-0.92, QP-1=0.02288 f-0.92, and QS-1=0.01647 f-0.91, QP-1=0.02826 f-0.97 in Baoshan, YLH, LY areas respectively. The attenuation of YLH, LY are closer to each other, however, Baoshan area is apparently lower. Comparing attenuation in the three areas with other areas of the world using the same method, it is suggested that the attenuations of P and S waves in YLH and LY areas are close to Kanto of Japan, but much higher than southeast of South Korea. The QS-1 and QP-1 in Baoshan area are slightly higher than southeastern South Korea. Furthermore, the results indicate that our QS-1 in Yunnan area is close to others by analyzing the coda attenuation.

SLC Analysis on Earthquake Activity in the Regions of Sichuan and Yunnan of China

Using the method of Single-link Cluster(SLC),analyzing the pattern of time sliding of SLCparameters,the earthquake activity in the western Sichuan-Yunnan of China is studiedcombining with the regional earthquake catalogue since 1970 and the tectonic background.Comparing with the high level of earthquake activity in 1970’s and the low in 1980’s,theearthquake activity is in general at the middle level in 1990’s.This paper suggests that SLCmethod,which considers the temporal and spatial relationship among earthquake events,could be adopted to analyze the trend of regional earthquake activity,it is very useful forstudying seismic activity.

Coordinated development of Yunnan's frontier culture and economy under the regional economic integration pattern

This paper constructs the index system by means of quantitative analysis. We choose the coordination degree of Yunnan province from 2012 to 2015. The regional cultural and economic development in Yunnan's frontier are analyzed so that we can provide the reference for the sustainable development of Yunnan's frontier and realize the coordinated development of culture in Yunnan's frontier and economic system in order. The results show that the culture and economy in Yunnan's frontier are coupled with formation of the coordinated development of culture and economy; economic development is the main reason to promote the coordinated development of culture and economy in Yunnan's frontier, and it contributes to the main force of improving the coordinated development of evolution types; the coordinated development degree of the overall level is low and still in the China's backward level.

The Spatial-temporal Distribution and Their Statistical Characteristics of Foreshocks in the Yunnan Region

We analyzed 223 earthquakes with M 1〉 5.0 that occurred in the Yunnan region during 1965 - 2014, among which 74 （ about 33. 2 % ） had foreshocks. There are great differences in foreshock populations in different tectonic blocks： the most abundant foreshocks occurred in the Lancang-Gengma and Tengchong-Baoshan blocks, which have the most abundant foreshocks in the Yunnan region. The predominant magnitude difference, time interval and spatial distance are 0. 5 -2. 9, within 10 days and within 20km, respectively. These characteristics can be used to forecast the mainshock after the identification of a foreshock.

Study on Eco-climate Type Regionalization of Wheat Growing Areas in Yunnan Province

In order to provide an objective and scientific theoretical basis for rational distribution of wheat growth in Yunnan Province,according to the relationship between Yunnan weather conditions and wheat growth adaptability,a study on eco-climate type regionalization of wheat growing areas in Yunnan was conducted using principal component analysis and GIS technology. The results show that Yunnan Province could be divided into four types,namely southern warm and humid wheat growing area,central semi-arid wheat growing area,central semi-humid wheat growing area and north-central cold wheat growing area.

Imaging 3-D crustal P-wave velocity structure of western Yunnan with bulletin data

Western Yunnan is a region with intensive tectonic activity and serious earthquake risk. It is of significant importance to study three dimensional crustal structure of this region to understand the tectonic setting and disaster mechanism. Densification and digitalization of seismic networks in this region provides an opportunity to study the velocity structure with bulletin data. In this study, we collect P-wave data of 10 403 regional earthquakes recorded by 79 seismic stations from January 2008 to December 2010. In addition to first arrivals data （Pg with epieentral distance less than 200 km and Pn）, the Pg （or P） data with epicentral distance more than 200 km are also considered as later direct arrivals in the tomographic inversion. We also compare the quantity and the quality of the seismic data before 2010 and after 2010. The test results show that adding the follow-up Pg phase can effectively improve the inversion ability of crustal imaging, and quantity and the data quality are significantly improved since 2010. The tomographie results show that： （1） The Honghe fault zone, which is the major fault systems in this region, may cut through the entire crust, and the velocity contrasts between two sides at lower crust beneath the Honghe fault are estimated at higher than 10%, while the velocity difference below Nujiang fault zone extends only in the upper crust; （2） Most of the earthquakes in the region occurred at the interface of high-velocity media and low-velocity media, i.e., the areas with high velocity gradient, which has been validated in other areas.

Waxy allele diversity in waxy maize landraces of Yunnan Province, China

Waxy maize is one of the main fresh-eating maize types,and a mutation of the waxy gene causes the waxy character of maize grains.China is rich in waxy maize landraces,and Yunnan and its surrounding areas,are the place of origin and genetic diversity center of Chinese waxy maize.The six known waxy alleles of Chinese waxy maize are wx-D7,wx-D10,wx-Cin4,wx-124,wx-Reina,and wx-Xuanwei.The mutation sites of these alleles all occur in the coding region of the waxy gene,however,the mechanism by which the waxy characteristic is caused by the mutation in the regulatory region has only been reported rarely in maize.In this study,405 waxy maize landraces from Yunnan were used as materials to identify the insertion and deletion of a large sequence fragment in the upstream~3.5 kb regulatory region of the waxy gene by molecular marker detection.Three different waxy alleles were identifed in this study:wx-PIF/Harbinger,wx-hAT and wxElote2.These three types of mutations all represented transposons inserted into the regulatory region of the waxy gene.Wx-PIF/Harbinger was a 304-bp MITE class transposon insertion belonging to the PIF/Harbinger family,while wx-hAT was a 560-bp MITE class transposon insertion belonging to the hAT family,and wx-Elote2 was a 6560-bp LTR-like transposon insertion.In this study,the alleles were identifed for more than 70%of the waxy maize landraces in Yunnan,which provids a basis for the utilization of these waxy maize landraces.

Study on medium-short term earthquake forecast in Yunnan Province by precursory events

The medium-short term forecast for a certain kinds of main earthquake events might be possible with the time-to-failure method presented by Varnes (1989), Bufe and Varnes (1993), which is to simulate an accelerative releasing model of precursory earthquake energy. By fitting the observed data with the theoretical formula, a medium-short term forecast technique for the main shock events could be established, by which the location, time and magnitude of the main shock could be determined. The data used in the paper are obtained from the earthquake catalogue recorded by Yunnan Regional Seismological Network with a time coverage of 1965~2002. The statistical analyses for the past 37 years show that the data of M2.5 earthquakes were fairly complete. In the present paper, 30 main shocks occurred in Yunnan region were simulated. For 25 of them, the forecasting time and magnitude from the simulation of precursory sequence are very close to the actual values with the precision of about 0.57 (magnitude unit). Suppose that the last event of the precursory sequence is known, then the time error for the forecasting main shock is about 0.64 year. For the other 5 main shocks, the simulation cannot be made due to the insufficient precursory events for the full determination of energy accelerating curve or disturbance to the energy-release curve. The results in the paper indicate that there is no obviously linear relation in the optimal searching radius for the main shock and the precursory events because Yunnan is an active region with damage earthquakes and moderate and small earthquakes. However, there is a strong correlation between the main shock moment and the coefficient k/m. The optimal fitting range for the forecasting time and magnitude can be further reduced using the relation between the main shock moment lgM0 and the coefficient lgk/m and the value range of the restricting index m, by which the forecast precision of the simulated main shock can be improved. The time-to-failure method is used to fit 30 main shocks in the paper and more than 80% of them have acquired better results, indicating that the method is prospective for its ability to forecast the known main shock sequence. Therefore, the prospect is cheerful to make medium-short term forecast for the forthcoming main shocks by the precursory events.

Development Trend and Mission of Yunnan Gardens

Development trend of Yunnan gardens are analyzed from domestic and international perspectives, and domestic opportunities for Yunnan gardens are explored. Concept, properties, location and significance of Yunnan gardens are introduced; the guiding concepts and development principles of Yunnan gardens are summarized. Through further study of Yunnan gardens, the authors promote the understanding of government and the public, research within academic circles, and applied practices by enterprises. Finally, development trend and mission of Yunnan gardens are discussed.