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Characteristics of S-wave Envelope Broadening in the changbaishan tianchi volcano

Earthquake Research in China 2010年第3期24卷 385-393页

作者： Fan Xiaoping Li Qinghe He Haibing Yang Congjie Jin Shumei Earthquake Administration of Jiangsu Province Nanjing 210014 China Earthquake Administration of Zhenjiang City Zhenjiang 212001 China

High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhomogeneities along the seismic ray path are the main causes of S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of the medium. The peak delay time of an S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify S-wave envelope broadening. 204 small earthquake records in changbaishan tianchi volcano were analyzed by the S-wave envelope broadening algorithm. The results show that S-wave envelope broadening in the changbaishan tianchi volcano is obvious,and that the peak delay time of S-wave has a positive correlation with the hypocenter distance and frequency of the S-wave. The relationships between the S-wave peak delay time and the hypocenter distance for different frequency bands were obtained using the statistics method. The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the changbaishan tianchi volcano region.

关键词： changbaishan tianchi volcano S-wave envelope broadening Peak delay timeof S-waves

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Heating Stage Experimental Study of Melt Inclusions in Feldspars from Three Holocene Eruptions of changbaishan tianchi volcano

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Earthquake Research in China 2008年第2期22卷 153-163页

作者： Li Ni Nicole Metrich Fan Qicheng Institute of Geology China Earthquake Administration Beijing 100029 China Laboratoire Pierre Sue CEA-CNRS Saclay 91191 Gif sur Yvette France

There occurred several eruptions from changbaishan tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. （Eruption Ⅰ ）, gray comenditic pumice and pyroclastic flow of - 1000a B.P. （ Eruption II, i.e. the millennium explosive eruption）, black trachy pumice and welded tuff of - 300a B.P. （ Eruption Ⅲ ） respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of changbaishan tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption H, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that （ 1 ） small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; （2） homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and （3） a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating.

关键词： changbaishan tianchi volcano Alkaline feldspar Melt inclusion Heating stage Homogenization temperature

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Recent Geochemical Variation of the Hot-Spring Gases from the tianchi volcano, Changbai Mountains, Northeast China

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Earthquake Research in China 2007年第2期21卷 179-188页

作者： Gao Ling Wei Haiquan Shangguan Zhiguan Wu Chengzhi Earthquake Administration of Beijing Municipality Beijing 100080 China Institute of Geology China Earthquake Administration Beijing 100029 China tianchi volcano Observatory （TVO） of changbaishan .lilin Antu 133613 China

Recent fluid monitoring work shows that the contents of mantle-derived CO2, He and CH4 increased anomalously in 2002 and 2003. The ^3He/^4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalously in 2003, and then decreased in 2004. The ^3He/^4He ratio from the thermal-reservoir-type Changbaijulong hot springs increased slowly in 2003, and the increase continued in 2004. The mantle-derived He content of the He released from the Changbaijulong springs increased obviously in 2004. The anomaly of the released gases and the isotopic He was consistent with the trends of seismic activities in the tianchi volcanic area between 2002 and 2004. The abnormal release of the Jinjiang hot springs apparently decreased after the seismic activities ceased in the second half of 2004, while the abnormal release from the Changbaljulong increased significantly after these seismic activities. It shows that the abnormal release of magmas-derived gases from the thermal-reservoir-type springs lags behind that of the deep-fault-type springs. These characteristics may be of great significance for identifying deep magmatic activity and predicting volcanic earthquakes in the future.

关键词： changbaishan tianchi volcano Volcanic earthquake Gas geochemistry

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