Yunnan Region Research Articles

Geographic distribution of the eastern honeybee, Apis cerana (Hymenoptera: Apidae), across ecological zones in China: Morphological and molecular analyses

The biogeography and intraspecific variability of the eastern cavity‐nesting honeybee, Apis cerana, are not very well known. We studied the variability of this species in China using morphometrical methods together with restriction and sequence analysis of two different regions of mitochondrial DNA. Samples of A. cerana were collected from feral or traditionally managed colonies in 19 locations of the Chinese mainland, covering the main ecological regions. Worker bees from each sample were dissected and morphometric characters were measured. The data were analysed with multivariate statistical procedures. Data were supplemented by previously published Chinese samples from the Oberursel data bank and reference samples of A. cerana from adjacent countries. A mitochondrial DNA fragment containing a non‐coding region was amplified and analysed with the restriction enzyme DraI. This fragment was sequenced for two samples. For a subset of samples, the subunit 2 of the mitochondrial NADH gene was amplified and sequenced. Morphometric analysis revealed a high degree of variation, strongly associated with ecological zones and correlated with geographical and climatic parameters. Two main clusters were apparent, one comprised the bees from the southern tropical seasonal rain forest region, showing strong associations to the bees of Vietnam, Thailand and Myanmar. The second main cluster included the bees from the temperate deciduous broad‐leaved forest region, the subtropical evergreen broad‐leaved forest zone, the high, cold meadow and steppe region and the North, and showed increasing similarity to the bees of Korea and Japan. In particular, the bees from Qingzang plateau, on the fringe of the Ganshu province, were set apart by their exceptional body size, darkness and pilosity. There was no variation in DraI restriction patterns within China. Sequence variation of the mitochondrial ND2 region was consistent with geographic patterns of morphological variation. Bees of the South Yunnan region were set apart by characteristically broad abdominal sterna and wax mirrors, with this locally restricted trait transcending the main transition line at the northern limit of the tropical seasonal rain forest region. This northern limit appears to correspond to the separation line between A cerana indica and A. cerana cerana.

Spatial distribution features of sequence types of moderate and strong earthquake in Chinese mainland

Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it takes mainshock-aftershock sequence type (MAT) as the major in Chuan-Dian rhombic block and concerned Xianshuihe-Anninghe-Xiaojiang seismic belt, as well as in Jinshajiang-Honghe seismic belt. Multiple mainshock type (MMT) mainly distributes in western Yunnan, and Longlin and Lancang areas in Tengchong-Baoshan block in west of Nujiang-Lancangjiang fault zone. A few isolated earthquake type (IET) mainly occurred in northwestern Sichuan and there is no IET occurred in Yunnan region. In northwestern China, it takes mainshock-aftershock sequence type (MAT) as the major in west segment of South Tianshan in Xinjiang region. Some MMT also occurred in this area in the intersection of Kalpin block and the Puchang fault zone. It takes IET as the major in middle Tianshan in Xinjiang. Along the Qilianshan seismic belt, most of sequences are MAT. In Qinghai region, it takes MAT as the major, but the regional feature of the spatial distribution of sequence types is not very clear. In North China, it takes MAT as the major in Yinshan-Yanshan-Bohai seismic belt, north edge of North China, and in Hebei plain seismic belt, as well as in sub-plate of lower river area of Yangtze River. In intersection of north segment of Shanxi seismic belt and the NW-trending Yinshan-Yanshan-Bohai seismic belt, there are several moderate or strong MMT with magnitude from 5.0 to 6.0 occurred. In south of North China around the latitude line of 35°N, it takes IET as the major. The spatial distribution of sequence types is relevant to the patterns of tectonic movements. MAT is mostly produced by the ruptures of locked units or asperities or the neonatal separating segments inside the fault zones. MMT is generally relevant to the conjugate structures or intersection of many tectonic settings. Further extension of simple fault often produces IET. Spatial distribution of sequence types is also correlative to the regional and deep environment of crustal medium to some extent. MAT mainly distributes in high velocity area in upper crust or in the transition zone between high velocity area and low velocity area, MMT mostly occurred in the low velocity area in upper crust.

Q value of anelastic S-wave attenuation in Yunnan region

Foundation item: Early-stage study project of the national key foundation research (2002CCD01700) and the key project of Yunnan Province during the 10th Five-year plan.

A Study on SKS Splitting Beneath the Yunnan Region, Southwestern China

AbstractSKS shear waves recorded at 47 stations in Yunnan and its vicinity are used to analyze the direction and extent of seismic anisotropy beneath this region. Some parameters on the dynamics of the Tibetan plateau, such as depth, thickness and origin of the anisotropy layer are discussed. The delay times vary from 0.58 to 1.88s in the study area. Fast polarization direction is nearly N‐S in the northern Yunnan, and gradually rotates to E‐W in the southern Yunnan. The shear wave splitting is mainly caused by the anisotropy layer in the upper mantle, whose thickness is between 67 and 216km. It is possible that the collision of India and Eurasian plates resulted in not only crustal thickening and subsequently the E‐W extension beneath the Tibetan plateau, but also mantle material flow southeastward.

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

We analyzed digital seismogram data of 5 668 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 Q S −1 and Q P −1 are expressed as Q S −1 =0.008 67 f −0.86, Q P −1 =0.011 55 f −0.93, Q S −1 =0.018 24 f −0.94, Q P −1 =0.022 88 f −0.92, and Q S −1 =0.016 47 f −0.91, Q P −1 =0.028 26 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 Q S −1 and Q P −1 in Baoshan area are slightly higher than southeastern South Korea. Furthermore, the results indicate that our Q S −1 in Yunnan area is close to others by analyzing the coda attenuation.

Constraining the extent of crust–mantle coupling in central Asia using GPS, geologic, and shear wave splitting data

We have obtained constraints on mechanical crust–mantle coupling for Tibet and Yunnan/Indo China, by comparing the observed surface deformation field inferred from GPS and Quaternary fault slip rate data, with the mantle deformation field inferred from several SKS shear wave splitting data sets. We first determined whether the anisotropy is dominantly asthenospheric or lithospheric by testing simple models of both types against the observed values of the fast polarization direction, ϕ, which is assumed to be parallel to the horizontal projection of the direction of maximum shear. For asthenospheric flow, we solved for a best-fitting uniform sub-asthenospheric velocity model for Eurasia. The fit, however, was not satisfactory (RMS misfit Δ ϕ = 20°). Solving for separate uniform flow fields in each region improves the fit (Δ ϕ = 15° for Tibet, Δ ϕ = 11° for Yunnan), although the resulting flow fields are inconsistent with several geophysical and geological constraints and thus considered unlikely. We then considered lithospheric models. For Tibet, vertically coherent deformation (i.e., maximum shear direction from surface deformation is parallel to ϕ) yields an improved match (Δ ϕ = 11°) for left-lateral shear. Both the goodness of fit and the dominance of left-lateral surface faulting in Tibet, argue for a lithospheric source of anisotropy. The misfit for Yunnan is large for either right- (Δ ϕ = 53°) or left-lateral (Δ ϕ = 49°) shear, which argues for complete crust–mantle decoupling in Yunnan. We show that the fast polarization directions throughout both the Tibet and Yunnan region can be fit by a single lithospheric dynamic model in which there is strong coupling between crust and mantle beneath Tibet, but a complete decoupling between crust and mantle beneath Yunnan crust. This dynamic model predicts left-lateral maximum shear directions within the mantle that align with fast polarization directions in both regions (Δ ϕ = 9°). These maximum shear directions within the mantle align with the left-lateral maximum shear directions in the crustal deformation field in Tibet, but are not in Yunnan. Our results have the following implications. First, the coherence between crust and mantle deformation in Tibet implies strong crust–mantle mechanical coupling, since this is the only way that crustal buoyancy forces, required to account for the surface deformation field, can be transmitted into the mantle. This behavior is consistent with a uniform-strength lithosphere or strong crust, but not with a substantially weaker crust. For example, it is inconsistent with the popular “jelly-sandwich” rheology, and thus precludes behavior such as large-scale lower crustal flow in Tibet. The crust–mantle coherence is also incompatible with mantle delamination. Second, crust–mantle decoupling within the Yunnan lithosphere argues that mantle deformation there is controlled only by boundary conditions; crustal buoyancy forces are not transmitted into the mantle beneath Yunnan. Moreover, the dynamic model for the mantle shows that the Yunnan crust is moving south with respect to the mantle at rates as high as ∼30 mm/yr. Third, there is a fundamental rheological lithospheric transition between Tibet and Yunnan that may provide a key to understanding this significant orogen.

3-D Velocity Structure of the Middle and Upper Crust in the Yunnan Region, China

Using short-period (1–18 s) surface wave data recorded by 23 stations of the Yunnan Digital Seismic Network of China we determined phase velocities of the fundamental Rayleigh wave along 209 paths by the two-station narrowband filtering and cross-correlation method, followed by an inversion for phase velocity distributions at various periods using the Ditmar-Yanovskaya method. We then obtained a 3-D S-wave velocity structure of the middle and upper crust in the Yunnan region using the genetic algorithm. The results show strong lateral variation of phase velocity in the region. The short-period phase velocity variation is closely related to thickness variation of sedimentary layer in the shallow crust. Within the depth range of 26–30 km, the S-wave velocity in the Sichuan-Yunnan rhombic block is lower than in the surrounding areas. Most large earthquakes of M > 6.0 in Yunnan occurred in the transition zones between low and high velocities.

S-wave velocity and Poisson’s ratio structure of crust in Yunnan and its implication

Receiver function of body wave under the 23 stations in Yunnan was extracted from 3-component broadband digital recording of teleseismic event. Thus, the S-wave velocity structure and distribution characteristics of Poisson’s ratio in crust of Yunnan are obtained by inversion. The results show that the crustal thickness is gradually thinned from north to south. The crustal thickness in Zhongdian of northwest reaches as many as 62.0 km and the one in Jinghong of further south end is only 30.2 km. What should be especially noted is that there exists a Moho upheaval running in NS in the Chuxiong region and a Moho concave is generally parallel to it in Dongchuan. In addition, there exists an obvious transversal inhomogeneity for the S-wave velocity structure in upper mantle and crust in the Yunnan region. The low velocity layer exists not only in 10.0-15.0 km in upper crust in some regions, but also in 30.0-40.0 km in lower crust. Generally, the Poisson’s ratio is on the high side, however it has a better corresponding relation to the crustal velocity structure. An obvious block distribution feature is still shown on such a high background of Poisson’s ratio. It is discovered by synthetically analyzing the velocity structure and Poisson’s ratio distribution that there are high Poisson’s ratio and complicated crust-mantle velocity structure feature in the Sichuan-Yunnan Diamond Block with Xiaojiang fault to be the east boundary and Yulong Snow Mountain fault to be the west boundary besides the frequent seismicity. This feature differs obviously from that of surrounding areas, which would provide geophysical evidence to deeply study the eastwardly flowage of lithospheric substances in the Qinghai-Tibet Plateau.

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 periods in Yunnan region are inverted. The maps of phase velocities on profiles along 24°N, 25°N, 26°N, 27°N and 100.5°E 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.

S‐Wave Velocity Structure of the Middle and Upper Crust Beneath the Yunnan Region

AbstractWe use dispersion data of phase velocities of the fundamental mode Rayleigh wave to inverse the S‐wave velocity structure of the middle and upper crust beneath the Yunnan region. The horizontal distribution maps of S‐wave velocities at four depths and S‐wave velocities on profiles along 24°N, 25°N, 26°N, 27°N and 100.5°E in the study region are presented. The results show that within the range of 26~30km depth, the S‐wave velocity in the Sichuan‐Yunnan rhombic block is obviously lower than that in surrounding areas. In the southern rhombic block, there is a low velocity area in the range from the ground to 15km depth. The epicentral locations of major earthquakes with M > 6.0 in the Yunnan region are closely related to the S‐wave velocity distribution. They are mainly distributed in zones of transition between low and high velocities.

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 ofM≥2.5 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 coefficientk/m. The “optimal fitting range“ for the forecasting time and magnitude can be further reduced using the relation between the main shock moment lgM 0 and the coefficientlgk/m and the value range of the restricting indexm, 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.

Image the Zhefang‐Binchuan and Monglian‐Malong Wide‐Angle Seismic Profiles in Yunnan Province

AbstractBased on the finite difference inversion and ray inversion method, the crust and upper mantle structure along the Zhefang–Binchuan and Menglian–Malong wide–angle seismic profiles, both of which are located in Yunnan province, are imaged using the geophysical data of travel‐time, amplitude ratio and Bouguer gravity anomalies. Thus some new recognitions about the geodynamics and the seismotectonic environment are derived. The crust thickness along the Zhefang–Binchuan profile is 35~46km, and that of the Menglian–Malong profile is 33~44.5km. The geometry of the Moho interface looks like that given by Hu H X et al. The P wave velocity on the top of the mantle beneath some places is relatively low and the variation range of the velocity is very large, which may indicates that the Yunnan region is a typical area of active tectonics. Moreover, there exits a prominent consistency between the shallow and deep structures, which implies that the activity of shallow material always has a deep background. The velocity structure of Zhefang–Binchuan profile indicates that there exists a large low velocity anomaly which penetrates the whole crust to the east of the Nujiang fault exposed on the ground, and this possibly associated with the upwelling of the deep material . The characteristic of the large faults which are the borders between some first order tectonic units can also be derived from the both velocity structure profiles: the Red River fault is a hyper‐fault that cuts the lithosphere, the Nujiang fault cuts deeply in the crust and even stretches downward into the top of the upper mantle, yet the Changning–Shuangjiang fault has a listric shape with a small dip angle, which may suggest that its incision depth is not very deep. The large earthquakes took place in Yunnan province always have a relationship with the large and deep faults that stretches into the upper mantle. Some earthquakes with shallow focal depths are generally located at the converge positions of different faults within the upper‐middle crust or the places where the velocity contours on the belt between the high and low velocity anomaly blocks are crooked. It is estimated that these locations are favorable to the accumulation of energy and regional stress.

The Archipelagic Ocean System of the Eastern Eurasian Tethys

Abstract Unlike typical oceans such as the wide and “clean” Atlantic, the Tethys has been showing an archipelagic pattern during all its evolutionary stages. Compared with the traditional, wedge‐shaped and relatively “clean” ocean model, the archipelagic model is more suitable for the Tethys, especially the eastern Tethys. This paper demonstrates the eastern Tethys archipelagic system in terms of the subdivision, characteristics and evolutionary history of the Qinling‐Qilian‐Kunlun, South China and Xizang (Tibet)‐Yunnan Regions of the eastern Eurasian Tethys.

Geological setting, nature of ore fluids and sulphur isotope geochemistry of the Fu Ning Carlin‐type gold deposits, Yunnan Province, China

AbstractCarlin‐type gold deposits in southern China are present in Palaeozoic to Mesozoic siliciclastic and carbonate rocks. The border region of Yunnan, Guizhou and Guangxi Provinces contains gold deposits on the south‐western margin of the Pre‐Cambrian South China Craton in south‐eastern Yunnan Province. The Fu Ning gold deposits host epigenetic, micron‐sized disseminated gold in: (i) Middle Devonian (D1p) black carbonaceous mudstone at the Kuzhubao gold deposit and (ii) fault breccia zones at the contact between Triassic gabbro (β\mathrm{\mu} ^{1}_{5}) and the Devonian mudstone (D1p) at the Bashishan gold deposit. The deposits are associated with zones of intense deformation with enhanced permeability and porosity that focused hydrothermal fluid flow, especially where low‐angle N‐S striking thrust faults are cut by NW striking strike‐slip and/or NE striking normal faults. Major sulphide ore minerals in the Fu Ning gold deposits are pyrite, arsenopyrite, arsenic‐rich pyrite, stibnite and minor iron‐poor sphalerite. Gangue minerals are quartz, sericite, calcite, ankerite and chlorite. Hypogene ore grades range from 1 to 7 g t−1 Au and up to 18 g t−1 Au at the Kuzhubao gold deposit and are generally less than 3 g t−1 Au at the Bashishan gold deposit. Sub‐microscopic gold mineralization is associated with finely disseminated arsenic‐rich pyrite in the Stage III mineral assemblage. Two types of primary fluid inclusions have been recorded: Type I liquid–vapour inclusions with moderate‐to‐high liquid/vapour ratios, and Type II inclusions containing moderate liquid/vapour ratios with CO2 as determined from laser Raman analysis. Temperature of homogenization (Th) data collected from these primary fluid inclusions in gold‐ore Stage III quartz ranged from 180 to 275°C at the Kuzhubao gold deposit and 210 to 330°C at the Bashishan gold deposit. Salinity results indicate that there were possibly two fluids present during gold deposition, including: (i) an early fluid with 0.8–6.5 wt.% NaCl equivalent, similar to salinity in shear‐zone‐hosted gold deposits with metamorphic derived fluids; and (ii) a late fluid with 11.8–13.4 wt.% NaCl equivalent, indicating possible derivation from connate waters and/or brine sources. CO2 and trace CH4 were only detected by laser Raman spectrometry in gold‐ore‐stage primary fluid inclusions. Results of sulphur isotope studies showed that δ34S values for pyrite and arsenopyrite associated with gold‐ore mineralization during Stage III at the Kuzhubao and Bashishan gold deposits are isotopically similar and moderately heavy with a range from +9 to +15 per mil, and also fall into the range of δ34S values reported for Carlin‐type gold deposits. Sulphur isotopes suggest that the Fu Ning gold deposits were formed from connate waters and/or basinal brines. Fluid geochemistry data from the Fu Ning gold deposits suggest a Carlin‐type genetic model, involving fluid mixing between: (i) deep CO2‐rich metamorphic fluids, (ii) moderately saline, reduced connate waters and/or basinal brines; and (iii) evolved meteoric waters.

Tomographic investigation of the upper crustal structure and seismotectonic environments in Yunnan Province

Investigation has been made for the upper crust structure and seismotectonic environments in Yunnan Province using the plentiful DSS data of the four profiles. The derived velocity model has a good relationship with the exposed basins, uplifts and faults. The low velocity anomaly corresponding to the volcano also has been revealed. There exits a prominent lateral inhomogeneity within the upper crust of Yunnan region. The depth of crystalline basement generally ranges from 0 km to 5 km, and the bedrocks are exposed on the ground directly in some places, nevertheless the thickness of sedimentary cover also can reach to 8 km or even 12 km at some large depressions. Although the Changning-Shuangjiang fault is a boundary between two first class tectonic units, its incision depth within the crust maybe shallow. On the other hand, known as the plates’ seam, the Honghe fault has a distinct evidence of extending into the mid-lower crust. The widely spread activity of the volcanoes in the geological era has a close relationship with the earthquake’s occurrence nowadays. Despite of the ceasing of the volcanoes in some places on the ground, the material in the mid-lower crust is still active, and there still exists strong upward stress. As the ceasing of the volcanoes on the surface, most parts of the power from the lower crust and the upper mantle cannot be released; therefore it accumulates at some appropriate tectonic locations. Moreover, the saturation of the water from the basin, the action of other fluids, and the effects of the outer stress maybe another direct reason account for the strong earthquakes’ occurrence in Yunnan region.

Primula calyptrata, a New Species in Section Carolinella (Primulaceae) from Yunnan, China

Primula calyptrata X. Gong & R. C. Fang (Primulaceae) is described and illustrated. Analysis of its habitat, distribution, and capsule morphology indicates that this species is a member of Primula sect. Carolinella (Helmsley) Pax, which is endemic to humid subtropical regions of Yunnan, China, northern Vietnam, and Thailand, and characterized by an unusual calyptrate capsule.

High Prevalence of HIV-1 and Hepatitis C Virus Coinfection Among Injection Drug Users in the Southeastern Region of Yunnan, China

High Prevalence of HIV-1 and Hepatitis C Virus Coinfection Among Injection Drug Users in the Southeastern Region of Yunnan, China

High prevalence of HIV-1 and hepatitis C virus coinfection among injection drug users in the southeastern region of Yunnan, China.

The southeastern region of Yunnan province is a key site for drug trafficking and HIV-1 infection spread from the west of Yunnan and Laos to southeastern China. To investigate the prevalence of HIV-1 infection and hepatitis C virus (HCV) coinfection among injection drug users (IDUs) in southeastern Yunnan, three cohorts of 285 addicts, including 242 IDUs and 43 oral drug users, living in the cities of Gejiu and Kaiyuan and the county of Yanshan were studied. HIV-1 and HCV infections were detected by enzyme-linked immunosorbent assay and/or polymerase chain reaction. Data on the age, sex, risk behavior, drug use history, employment, ethnic background, and marriage status were obtained by interview. The overall prevalence of HIV-1 infection was 71.9%. The rate of HCV coinfection among 138 HIV-1-infected IDUs was 99.3%. Most HIV-infected IDUs were 20 to 35 years old (86.7%) and were ethnic Han (75.9%), suggesting that the epidemic in Yunnan is no longer confined to non-Han ethnic minorities. HIV prevalence in female IDUs (81.2%) was significantly higher than in male IDUs (68.2%) ( p <.05). The prevalence of HIV infection reached 68.4% after 1 year of injection drug use. Needle/syringe sharing is the major high risk factor for the spread of HIV-1 and HCV infections. Large-scale educational campaigns are urgently needed to reduce the spread of HIV and HCV infection in these regions.

Allegorising the Local on the Borderland: Ai Wu's Nanxingji and National Subjectivity

AbstractThis paper offers a reading of Ai Wu's Nanxingji series (Trilogy of Travel Through the South) depicting the author's journey from Yunnan to Burma in the May Fourth era and his subsequent returns to the border regions of Yunnan in the socialist period. It explores the ways in which allegorical dimensions of ‘the local’ shift at different social-historical junctures: ‘the local’ as a site in need of reforms in the 1920s, in socialist reality in the early 1960s, and in traumatic memories of the Cultural Revolution in the early 1980s. In extrapolating these ‘local’ dimensions embedded in the Nanxingji series, this paper suggests a contingent rather than a causal relationship between national incorporation and ‘the local’ formations. Additionally, this paper highlights how travel operates as an allegorical device, linking ‘the personal’ to the interplay of local specificities and the national imaginary, and how travel styles themselves change over time.

S Wave Velocity Structure Beneath Digital Seismic Stations of Yunnan Province Inferred from Teleseismic Receiver Function Modeling

AbstractThe S wave velocity structure within the depth of 0‐100 km beneath digital seismic stations of Yunnan Province was obtained from teleseismic receiver function modeling. The results show that the crustal thickness changes greatly in Yunnan, reaching about 62 km in Zhongdian and Lijiang, and decreasing to 32‐34 km in Jinghong, Simao and Changyuan in south. The thick crust extends from northwest to southeast, decreases in thickness and range, and is about 42 km thick around Tonghai. Its shape and range consist with Chuandian diamond block bounded by Xiaojiang and Yuanjiang faults. In the eastern and southern region, the crust is relatively thin, and the velocity contrast across Moho is obvious. In the areas with great variation of crustal thickness or thick crust area, the Moho is characterized by transition zone with high velocity gradient. In Yunnan region, S wave velocity structures show strong horizontal heterogeneity. Above the depth of 10 km, the S wave velocity in north area is obviously lower than that in south area, while within the depth of 10‐20 km, the S wave velocity in north is higher than that in south. The velocity interface within crust is discontinuous, and the depth and range of lower velocity zones change with different seismic stations. There is no obvious crustal low velocity zone beneath nearly half of the stations. Influenced by the upper mantle in south area, within the depth of 40‐50 km, S wave velocity in south area is higher than that in north, high velocity area extends to north, and the shape of low velocity zone tends to consist with Chuandian diamond block. The upper mantle velocity distribution within the depth of 70‐80 km seems to be correlated to the distribution of strong earthquakes.