Advanced Search

EPP

地球与行星物理

ISSN  2096-3955

CN  10-1502/P

Citation: Mei Li, Li Yao, YaLi Wang, Michel Parrot, Masashi Hayakawa, Jun Lu, HanDong Tan, Tao Xie, 2019: Anomalous phenomena in DC–ULF geomagnetic daily variation registered three days before the 12 May 2008 Wenchuan MS 8.0 earthquake, Earth and Planetary Physics, 3, 330-341. doi: 10.26464/epp2019034

2019, 3(4): 330-341. doi: 10.26464/epp2019034

SOLID EARTH: GEOELECTROMAGNETICS

Anomalous phenomena in DC–ULF geomagnetic daily variation registered three days before the 12 May 2008 Wenchuan MS 8.0 earthquake

1. 

China Earthquake Networks Center, China Earthquake Administration, Beijing 100045, China

2. 

Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Université d’Orléans, CNRS, Orléans, France

3. 

Hayakawa Institute of Seismo Electromagnetics, Co. Ltd., University of Electro–Communications (UEC), Chofu, Japan

4. 

UEC, Advanced Wireless Communications Research Center, Chofu, Japan

5. 

School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China

Corresponding author: Mei Li, mei_seis@163.com

Received Date: 2019-01-05
Web Publishing Date: 2019-07-01

The hourly data of the vertical Z and the horizontal H components of 37 ground–based DC–ULF geomagnetic stations are examined during 20 April–12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies — a double low-point and a decreased amplitude — are registered on the curves of the Z component at 25 stations in a large-scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low-point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift (Tzs) between the first low-point on May 9 and the minimum point occurring time of May 1–5, 2008 is also checked. The results show that Tzs is on the order of 1–2 hours earlier or later than usual and there is a 2–6 hours’ gap between these two low-points. However, there is still a transition area which includes the epicenter where Tzs = 0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth–air–ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above-related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan MS 8.0 earthquake.

Key words: Wenchuan MS 8.0 earthquake, geomagnetic abnormity, spatial variations, Earth–air–ionosphere model

Akhoondzadeh, M., Parrot, M., and Saradjian, M. R. (2010). Electron and ion density variations before strong earthquakes (M>6.0) using DEMETER and GPS data. Nat. Hazards Earth Syst. Sci., 10(1), 7–18. https://doi.org/10.5194/nhess-10-7-2010

Bernardi, A., Fraser-Smith, A. C., McGill, P. R., and Villard, Jr. O. G. (1991). ULF magnetic field measurements near the epicenter of the MS 7.1 Loma Prieta earthquake. Phys. Earth Planet. Interiors, 68(1-2), 45–63. https://doi.org/10.1016/0031-9201(91)90006-4

Fraser-Smith, A. C., Bernardi, A., McGill, P. R., Ladd, M. E., Helliwell, R. A., and Villard, Jr. O. G. (1990). Low-frequency magnetic field measurements near the epicenter of the MS 7.1 Loma Prieta earthquake. Geophys. Res. Lett., 17(9), 1465–1468. https://doi.org/10.1029/GL017i009p01465

Gao, S. D., Tang, J., Du, X. B., Liu, X. F., Su, Y. G., Chen, Y. P., Di, G. R., Mei, D. L., Zhan, Y., and Wang, L. F. (2010). The change characteristics of electromagnetic field before to after Wenchuan MS 8.0 earthquake. Chinese J. Geophys. (in Chinese) , 53(3), 512–525. https://doi.org/10.3969/j.issn.0001-5733.2010.03.005

Hasegawa, M. (1960). On the position of the focus of the geomagnetic S q current system. J. Geophys. Res., 65(5), 1437–1447. https://doi.org/10.1029/JZ065i005p01437

Hayakawa, M., Kawate, R., Molchanov, O. A., and Yumoto, K. (1996). Results of ultra-low-frequency magnetic field measurements during the Guam earthquake of 8 August 1993. Geophys. Res. Lett., 23(3), 241–244. https://doi.org/10.1029/95GL02863

Hayakawa, M., Kasahara, Y., Nakamura, T., Muto, F., Horie, T., Maekawa, S., Hobara, Y., Rozhnoi, A. A., Solovieva, M., and Molchanov, O. A. (2010). A statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric VLF/LF propagation and earthquakes. J. Geophys. Res. Space Phys., 115(A9), A09305. https://doi.org/10.1029/2009JA015143

Hayakawa, M. (2015). Earthquake Prediction with Radio Techniques. Aviation International News, 42. https://doi.org/10.1002/9781118770368

Hayakawa, M., Schekotov, A., Potirakis, S. M., and Eftaxias, K. (2015a). Criticality features in ULF magnetic fields prior to the 2011 Tohoku earthquake. Proc. Japan Acad. Ser. B, 91(1), 25–30. https://doi.org/10.2183/pjab.91.25

Hayakawa, M., Schekotov, A., Potirakis, S. M., Eftaxias, K., Li, Q., and Asano, T. (2015b). An integrated study of ULF magnetic field variations in association with the 2008 Sichuan Earthquake, on the basis of statistical and critical analyses. Open J. Earthq. Res., 4(3), 85–93. https://doi.org/10.4236/ojer.2015.43008

Hu, J. C., Liu, W., Guo, M. R., and Zheng, H. (2009). The " double low-points” anomaly of daily vertical component variation of geomagnetic field before the M8.0 Wenchuan earthquake. Acta Seismol. Sin. (in Chinese) , 31(5), 589–593. https://doi.org/10.3321/j.issn:0253-3782.2009.05.012

Kawate, R., Molchanov, O. A., and Hayakawa, M. (1998). Ultra-low-frequency magnetic fields during the Guam earthquake of 8 August 1993 and their interpretation. Phys. Earth Planet. Interiors, 105(3-4), 229–238. https://doi.org/10.1016/S0031-9201(97)00094-0

Kopytenko, Y. A., Matiashvili, T. G., Voronov, P. M., Kopytenko, E. A., and Molchanov, O. A. (1993). Detection of ultra-low-frequency emissions connected with the Spitak earthquake and its aftershock activity, based on geomagnetic pulsations data at Dusheti and Vardzia observatories. Phys. Earth Planet. Interiors, 77(1-2), 85–95. https://doi.org/10.1016/0031-9201(93)90035-8

Kuo, C. L., Huba, J. D., Joyce, G., and Lee, L. C. (2011). Ionosphere plasma bubbles and density variations induced by pre-earthquake rock currents and associated surface charges. J. Geophys. Res. Space Phys., 116(A10), A10317. https://doi.org/10.1029/2011JA016628

Kuo, C. L., Lee, L. C., and Huba, J. D. (2014). An improved coupling model for the lithosphere-atmosphere-ionosphere system. J. Geophys. Res. Space Phys., 119(4), 3189–3205. https://doi.org/10.1002/2013JA019392

Li, M., Lu, J., Su, X. Z., and Feng, Z. S. (2009). A study on fractal Brownian motion of geomagnetic observations before large earthquakes. Acta Seismol. Sin. (in Chinese) , 31(6), 650–659. https://doi.org/10.3321/j.issn:0253-3782.2009.06.006

Li, M., and Parrot, M. (2012). " Real time analysis” of the ion density measured by the satellite DEMETER in relation with the seismic activity. Nat. Hazards Earth Syst. Sci., 12(9), 2957–2963. https://doi.org/10.5194/nhess-12-2957-2012

Li, M., Lu, J., Parrot, M., Tan, H. D., Chang, Y., Zhang, X. D., and Wang, Y. L. (2013). Review of unprecedented ULF electromagnetic anomalous emissions possibly related to the Wenchuan MS = 8.0 earthquake, on 12 May 2008. Nat. Hazards Earth Syst. Sci., 13(2), 279–286. https://doi.org/10.5194/nhess-13-279-2013

Li, M., and Parrot, M. (2013). Statistical analysis of an ionospheric parameter as a base for earthquake prediction. J. Geophys. Res. Space Phys., 118(6), 3731–3739. https://doi.org/10.1002/jgra.50313

Li, M., Tan, H. D., and Cao, M. (2016). Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan MS 8.0 earthquake. Solid Earth, 7(5), 1405–1415. https://doi.org/10.5194/se-7-1405-2016

Li, Q., Schekotov, A., Asano, T., and Hayakawa, M. (2015). On the anomalies in ULF magnetic field variations prior to the 2008 Sichuan earthquake. Open J. Earthq. Res., 4(2), 55–64. https://doi.org/10.4236/ojer.2015.42005

Liu, J., Huang, J. P., and Zhang, X. M. (2014). Ionospheric perturbations in plasma parameters before global strong earthquakes. Adv. Space Res., 53(5), 776–787. https://doi.org/10.1016/j.asr.2013.12.029

Liu, J. Y., Chen, Y. I., Chen, C. H., Liu, C. Y., Chen, C. Y., Nishihashi, M., Li, J. Z., Xia, Y. Q., Oyama, K. I., … Lin, C. H. (2009). Seismoionospheric GPS total electron content anomalies observed before the 12 May 2008 Mw 7.9 Wenchuan earthquake. J. Geophys. Res. Space Phys., 114(A4), A04320. https://doi.org/10.1029/2008JA013698

Liu, J. Y., Chen, Y. I., Chuo, Y. J., and Tsai, H. F. (2001). Variations of ionospheric total electron content during the Chi-Chi earthquake. Res. Lett., 28, 1383–1386. https://doi.org/10.1029/2000GL012511

Lu, J., Xie, T., Li, M., Wang, Y. L., Ren, Y. X., Gao, S. D., Wang, L. W., and Zhao, J. L. (2016). Monitoring shallow resistivity changes prior to the 12 May 2008 M8.0 Wenchuan earthquake on the Longmen Shan tectonic zone, China. Tectonophysics, 675, 244–257. https://doi.org/10.1016/j.tecto.2016.03.006

Molchanov, O. A., Kopytenko, Y. A., Voronov, P. M., Kopytenko, E. A., Matiashvili, T. G., Fraser-Smith, A. C., and Bernardi, A. (1992). Results of ULF magnetic field measurements near the epicenters of the Spitak (MS 6.9) and Loma Prieta (MS 7.1) earthquakes: comparative analysis. Geophys. Res. Lett., 19(14), 1495–1498. https://doi.org/10.1029/92GL01152

Molchanov, O. A., and Hayakawa, M. (2008). Seismo Electromagnetics and Related Phenomena: History and Latest Results (pp. 189). Tokyo: TERRAPU.222

Obiekezie, T. N., and Okeke, F. N. (2010). External S q currents in the West African region. Moldavian J. Phys. Sci., 9(1), 117–122.

Obiekezie, T. N., Obiadazie, S. C., and Agbo, G. A. (2013). Day-to-day variability of H and Z components of the geomagnetic field at the African Longitudes. ISRN Geophys., 2013, 909258. https://doi.org/10.1155/2013/909258

Pan, H., Zhang, J. G., Yang, D. M., and Li, M. (2014). A possible mechanism of the contributing factor of geomagnetic lowest shift. J. Geod. Geodyn. (in Chinese) , 34(4), 83–87. https://doi.org/10.14075/j.jgg.2014.04.029

Parrot, M. (2013). Satellite observations of ionospheric perturbations related to seismic activity. In M. Hayakawa (Ed.), Earthquake Prediction Studies: Seismo Electromagnetics (pp. 1-16). Tokyo: TERRAPUB.222

Prattes, G., Schwingenschuh, K., Eichelberger, H. U., Magnes, W., Boudjada, M., Stachel, M., Vellante, M., Villante, U., Wesztergom, V., and Nenovski, P. (2011). Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L’Aquila regarding regional geotechnical information. Nat. Hazards Earth Syst. Sci., 11(7), 1959–1968. https://doi.org/10.5194/nhess-11-1959-2011

Pulinets, S. A., and Boyarchuk, K. (2004). Ionospheric Precursors of Earthquakes. Berlin: Springer. https://doi.org/10.1007/b137616222

Rikitake, T. (1966). Electromagnetism and the Earth's Interior. Amsterdam, London, New York: Elsevier Publishing Company.222

Rikitake, T. (1973). Global electrical conductivity of the Earth. Phys. Earth Planet. Interiors, 7(3), 245–250. https://doi.org/10.1016/0031-9201(73)90051-4

Schekotov, A., Zhou, H. J., Qiao, X. L., and Hayakawa, M. (2016). ULF/ELF atmospheric radiation in possible association to the 2011 Tohoku earthquake as observed in China. Earth Sci. Res., 5(2), 47–58. https://doi.org/10.5539/esr.v5n2p47

Schekotov, A. Y., Fedorov, E., Molchanov, O. A., and Hayakawa, M. (2013). Low frequency electromagnetic precursors as a prospect for earthquake prediction. In M. Hayakawa (Ed.), Earthquake Prediction Studies: Seismo Electromagnetics (pp. 81-99). Tokyo: TERRAPUB.222

Varotsos, P. A., Sarlis, N. V., Tanaka, H. K., and Skordas, E. S. (2005). Similarity of fluctuations in correlated systems: the case of seismicity. Phys. Rev. E, 72(4), 041103. https://doi.org/10.1103/PhysRevE.72.041103

Wang, W. X., Ding, J. H., Yu, S. R., and Zhang, Y. X. (2009). Short-term and imminent geomagnetic anomalies of the Wenchuan Ms8.0 earthquake and exploration of earthquake prediction. Acta Seismol. Sin. (in Chinese) , 31(2), 172–179. https://doi.org/10.3321/j.issn:0253-3782.2009.02.006

Wang, X. M., Teng, Y. T., Wang, X. Z., Wang, C., and Wu, Q. (2008). The test method for the performance of fluxgate magnetometer. Seismol. Geomagn. Obs. Res. (in Chinese) , 29(6), 88–94. https://doi.org/10.3969/j.issn.1003-3246.2008.06.016

Xu, X. W. (2009). Album of 5.12 Wenchuan 8.0 Earthquake Surface Ruptures (in Chinese). Beijing: Seismological Press.222

Xu, T., Hu, Y. L., Wu, J., Wu, Z. S., Suo, Y. C., and Feng, J. (2010a). Giant disturbance in the ionospheric F2 region prior to the M8.0 Wenchuan earthquake on 12 May 2008. Ann. Geophys., 28(8), 1533–1538. https://doi.org/10.5194/angeo-28-1533-2010

Xu, T., Hu, Y. L., Wu, J., Wu, Z. S., Suo, Y. C., Feng, J., and Huang, C. J. (2010b). Abnormal perturbations in the ionospheric F2 region before Wenchuan earthquake on 12 May 2008. Sci. China Earth Sci., 53(11), 1671–1674. https://doi.org/10.1007/s11430-010-4046-4

Yu, T., Mao, T., Wang, Y. G., and Wang, J. S. (2009). Study of the ionospheric anomaly before the Wenchuan earthquake. Chinese Sci. Bull., 54(6), 1080–1086. https://doi.org/10.1007/s11434-008-0587-8

Zeng, Z. C., Zhang, B., Fang, G. Y., Wang, D. F., and Yin, H. J. (2009). The analysis of ionospheric variations before Wenchuan earthquake with DEMETER data. Chinese J. Geophys. (in Chinese) , 52(1), 11–19.

Zhang, X. M., Qian, J. D., Wang, Y. L., Zhao, X., Ouyang, X. Y., and Zhao, S. F. (2008). Spectral features of geomagnetic low point displacement and discussion on its mechanism. Acta Seismol. Sin. (in Chinese) , 30(5), 474–483. https://doi.org/10.3321/j.issn:0253-3782.2008.05.005

Zhao, B., Yu, T., Wang, M. Wan, W., Lei, J., Liu, L., and Ning, B (2008). Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake?. J. Geophys. Res., 113, A11304. https://doi.org/10.1029/2008JA013613

Zhang, X. M., Shen, X. H., Liu, J., Ouyang, X. Y., Qian, J. D., and Zhao, S. F. (2009a). Analysis of ionospheric plasma perturbations before Wenchuan earthquake. Nat. Hazards Earth Syst. Sci., 9(4), 1259–1266. https://doi.org/10.5194/nhess-9-1259-2009

Zhang, X. M., Ding, J. H., Shen, X. H., Wang, M., Liu, J., Yu, S. R., Wang, Y. L., and Ouyang, X. Y. (2009b). Electromagnetic perturbations before Wenchuan M8 earthquake and stereo electromagnetic observation system. Chinese J. Radio Sci. (in Chinese) , 24(1), 1–8. https://doi.org/10.3969/j.issn.1005-0388.2009.01.001

Zhang, X. M., Shen, X. H., Liu, J., Ouyang, X. Y., Qian, J. D., and Zhao, S. F. (2010). Ionospheric perturbations of electron density before the Wenchuan Earthquake. Int. J. Remote Sens., 31(13), 3559–3569. https://doi.org/10.1080/01431161003727762

Zhang, Y., Feng, W. P., Xu, L. S., Zhou, C. H., and Chen, Y. T. (2009). Spatio-temporal rupture process of the 2008 great Wenchuan earthquake. Sci. China Ser. D: Earth Sci., 52(2), 145–154. https://doi.org/10.1007/s11430-008-0148-7

Zhu, F. Y., Wu, Y., Lin, J., Zhou, Y. Y., Xiong, J. and Yang, J. (2009). Anomalous response of ionospheric VTEC before the Wenchuan earthquake. Acta Seismol. Sin. (in Chinese) , 31(2), 180–187. https://doi.org/10.3321/j.issn:0253-3782.2009.02.007

[1]

YaLi Wang, Tao Xie, YanRu An, Chong Yue, JiuYang Wang, Chen Yu, Li Yao, Jun Lu, 2019: Characteristics of the coseismic geomagnetic disturbances recorded during the 2008 Mw 7.9 Wenchuan Earthquake and two unexplained problems, Earth and Planetary Physics. doi: 10.26464/epp2019043

[2]

LiSheng Xu, Xu Zhang, ChunLai Li, 2018: Which velocity model is more suitable for the 2017 MS7.0 Jiuzhaigou earthquake?, Earth and Planetary Physics, 2, 163-169. doi: 10.26464/epp2018016

[3]

Xu Zhang, Zhen Fu, LiSheng Xu, ChunLai Li, Hong Fu, 2019: The 2018 MS 5.9 Mojiang Earthquake: Source model and intensity based on near-field seismic recordings, Earth and Planetary Physics, 3, 268-281. doi: 10.26464/epp2019028

[4]

Feng Long, GuiXi Yi, SiWei Wang, YuPing Qi, Min Zhao, 2019: Geometry and tectonic deformation of the seismogenic structure for the 8 August 2017 MS 7.0 Jiuzhaigou earthquake sequence, northern Sichuan, China, Earth and Planetary Physics, 3, 253-267. doi: 10.26464/epp2019027

[5]

BoJing Zhu, Hui Yan, David A Yuen, YaoLin Shi, 2019: Electron acceleration in interaction of magnetic islands in large temporal-spatial turbulent magnetic reconnection, Earth and Planetary Physics, 3, 17-25. doi: 10.26464/epp2019003

[6]

Tong Dang, JiuHou Lei, XianKang Dou, WeiXing Wan, 2017: A simulation study of 630 nm and 557.7 nm airglow variations due to dissociative recombination and thermal electrons by high-power HF heating, Earth and Planetary Physics, 1, 44-52. doi: 10.26464/epp2017006

[7]

Bin Zhuang, YuMing Wang, ChengLong Shen, Rui Liu, 2018: A statistical study of the likelihood of a super geomagnetic storm occurring in a mild solar cycle, Earth and Planetary Physics, 2, 112-119. doi: 10.26464/epp2018012

[8]

Tian Tian, Zheng Chang, LingFeng Sun, JunShui Bai, XiaoMing Sha, Ze Gao, 2019: Statistical study on interplanetary drivers behind intense geomagnetic storms and substorms, Earth and Planetary Physics. doi: 10.26464/epp2019039

[9]

WeiXing Wan, 2017: Earth science, planetary vision——A foreword to Earth and Planetary Physics (EPP), Earth and Planetary Physics, 1, 1-1. doi: 10.26464/epp2017001

[10]

MeiJuan Yao, Jun Cui, XiaoShu Wu, YingYing Huang, WenRui Wang, 2019: Variability of the Martian ionosphere from the MAVEN Radio Occultation Science Experiment, Earth and Planetary Physics, 3, 283-289. doi: 10.26464/epp2019029

[11]

Yong Wei, XinAn Yue, ZhaoJin Rong, YongXin Pan, WeiXing Wan, RiXiang Zhu, 2017: A planetary perspective on Earth’s space environment evolution, Earth and Planetary Physics, 1, 63-67. doi: 10.26464/epp2017009

[12]

TianYu Zheng, YongHong Duan, WeiWei Xu, YinShuang Ai, 2017: A seismic model for crustal structure in North China Craton, Earth and Planetary Physics, 1, 26-34. doi: 10.26464/epp2017004

[13]

Jing Huang, Meng Zhou, HuiMin Li, XiaoHua Deng, Jiang Liu, ShiYong Huang, 2019: Small-scale dipolarization fronts in the Earth′s magnetotail, Earth and Planetary Physics, 3, 358-364. doi: 10.26464/epp2019036

[14]

TianJun Zhou, Bin Wang, YongQiang Yu, YiMin Liu, WeiPeng Zheng, LiJuan Li, Bo Wu, PengFei Lin, Zhun Guo, WenMin Man, Qing Bao, AnMin Duan, HaiLong Liu, XiaoLong Chen, Bian He, JianDong Li, LiWei Zou, XiaoCong Wang, LiXia Zhang, Yong Sun, WenXia Zhang, 2018: The FGOALS climate system model as a modeling tool for supporting climate sciences: An overview, Earth and Planetary Physics, 2, 276-291. doi: 10.26464/epp2018026

[15]

YiJian Zhou, ShiYong Zhou, JianCang Zhuang, 2018: A test on methods for MC estimation based on earthquake catalog, Earth and Planetary Physics, 2, 150-162. doi: 10.26464/epp2018015

[16]

XueMei Zhang, GuangBao Du, Jie Liu, ZhiGao Yang, LiYe Zou, XiYan Wu, 2018: An M6.9 earthquake at Mainling, Tibet on Nov.18, 2017, Earth and Planetary Physics, 2, 84-85. doi: 10.26464/epp2018009

[17]

Yi-Ching Lo, Li Zhao, XiWei Xu, Ji Chen, Shu-Huei Hung, 2018: The 13 November 2016 Kaikoura, New Zealand earthquake: rupture process and seismotectonic implications, Earth and Planetary Physics, 2, 139-149. doi: 10.26464/epp2018014

[18]

WeiMin Wang, JianKun He, JinLai Hao, ZhenXing Yao, 2018: Preliminary result for the rupture process of Nov.13, 2017, Mw7.3 earthquake at Iran-Iraq border, Earth and Planetary Physics, 2, 82-83. doi: 10.26464/epp2018008

[19]

ZhiKun Ren, ZhuQi Zhang, PeiZhen Zhang, 2018: Different earthquake patterns for two neighboring fault segments within the Haiyuan Fault zone, Earth and Planetary Physics, 2, 67-73. doi: 10.26464/epp2018006

[20]

HaiLin Du, Xu Zhang, LiSheng Xu, WanPeng Feng, Lei Yi, Peng Li, 2018: Source complexity of the 2016 MW7.8 Kaikoura (New Zealand) earthquake revealed from teleseismic and InSAR data, Earth and Planetary Physics, 2, 310-326. doi: 10.26464/epp2018029

Article Metrics
  • PDF Downloads()
  • Abstract views()
  • HTML views()
  • Cited by(0)
Catalog

Figures And Tables

Anomalous phenomena in DC–ULF geomagnetic daily variation registered three days before the 12 May 2008 Wenchuan MS 8.0 earthquake

Mei Li, Li Yao, YaLi Wang, Michel Parrot, Masashi Hayakawa, Jun Lu, HanDong Tan, Tao Xie