云南腾冲地区现代地热流体活动类型

腾冲地区存在两类地热流体活动。其中热海- 热水塘地区、马鞍山火山口附近的地热流体活动属火山区地热流体活动,其热源或气体挥发组分的物质来源与近代火山喷发活动或现代幔源岩浆侵入活动直接有关。区内其它地热流体活动多属构造活动成因。在腾冲地区,地热流体逸出He 的3 He/4 He≥1-2 Ra 可作为区别这两类地热流体的可靠指标     

五大连池火山区的地震活动特征及其成因的初步探讨

通过对1981～1988年这一时期内五大连池火山区的地震和人工爆破记录的分析和整理,讨论了本区的岩浆侵入活动,总结了本区的地震活动特征,并对本区内地震活动成因机制进行了初步的探讨。结果表明:五大连池火山活动与地震活动存在着密切的联系,它们有着共同的成因机制即本区的岩浆侵入活动,火山区地震活动的不同特征反映着火山的活动性。火山区的小震及微震是由于岩浆侵入时期岩浆充填地下微裂隙和岩浆回落时期穹窿塌陷所致;火山区外围的中强地震是由于岩浆侵入活动诱发了讷木尔河深大断裂所致。     

腾冲火山区形变分析

腾冲火山群是我国目前仍具喷发危险的火山群。本文首先对火山区的地壳运动背景进行了总结分析,然后介绍了火山区的形变监测情况,再依据1998～2004年的水准测量及2002～2004年GPS观测成果,参考重力变化及其它观测资料分析火山区岩浆的活动特征,最后得出主要结论:相对欧亚板块,腾冲火山区总体具有向西南的顺时针旋转运动;火山区的形变变化受岩浆和断层活动两方面控制;火山区西南部发生了较强烈的下沉运动,可能由于岩浆和水的流失及放气等原因引起;以固东—腾冲断裂的西支为界,水平位移在断层两侧分别向东西两个方向运动,2002～2003年运动更剧烈些,断层活动表现为明显的拉张特征。综合各种资料表明火山目前活动量较小,近期喷发的危险性不大。     

长白山天池火山地热区逸出气体的物质来源

根据天池火山地热区逸出气体的化学成分和稳定同位素组成,讨论了这些气体的物质来源.提出该区逸出气体主要源自壳内幔源岩浆残留体;长白地热区可能与古火山喷发通道相连,其下方有一稳定的地热水和深源气储库,储库热水温度约(166±9)℃;锦江地热区逸出气体可能是通过活动构造带快速由深部向地表迁移的.     

中国火山温泉气体地球化学特征及其在火山监测中的应用

中国火山温泉主要分布在吉林长白山、云南腾冲和黑龙江五大连池等火山区。这些火山虽然处于休眠状态,但大面积的温泉分布指示着岩浆房存在的可能性。本文总结了前人研究成果,分析了中国主要火山区温泉气体地球化学特征,并探讨了温泉气体在火山监测中的应用。长白山、腾冲和五大连池火山区温泉气体地球化学性质类似,都以CO₂为主要气体,含量在80%以上,最高可达99%以上,其它气体组分包括CH₄、N₂、O₂、SO₂、H₂S、He和H₂等。长白山火山温泉气体中氦同位素比值（3He/4He）最高,约为4—6R_A,CO₂中碳同位素比值（δ13C）为-7.9‰—-1.3‰,CH₄中碳同位素为-48.0‰—-28.7‰;腾冲火山温泉气体氦同位素比值为3—5.5R_A,CO₂中的碳同位素为-6.49‰—-2.07‰,CH₄中碳同位素为-23.5‰—-9.3‰;五大连池火山温泉气体氦同位素比值约为3R_A,CO₂中的碳同位素比值为-9.6‰—-3.1‰,CH₄中碳同位素为-47.2‰—-44.4‰。3个火山区的温泉气体均显示地幔来源的岩浆气体特征,并在上升运移过程中受地壳或古俯冲物质的影响。     

2002年夏季长白山天池火山区的地震活动研究

2002年6月以来,长白山天池火山区的地震活动明显增加. 本文利用2002年夏季布设在长白山天池火山区15套宽频带流动地震台站的记录资料,对天池火山区的地震活动进行了研究. 地震观测结果表明,2002年夏季长白山天池火山日平均地震发生频次超过30次. 地震主要位于长白山天池西南部和东北部两个区域,震源深度较浅,离地表的深度一般小于5km. 天池西南部和东北部的地震,b值存在较大的差异. 火山区地震记录的频谱分析和时频分析结果表明,这些地震主要为火山构造型地震. HSZ和DZD等台站地震记录中丰富的低频成分,可能与台站附近的局部介质或断层带有关. 我们认为2002年夏季频繁发生的地震和小震震群活动是由火山深部活动诱发的局部断裂活动引起.     

Mogi模型在长白山天池火山区的应用

文中首先介绍了Mogi模型的阻尼最小二乘反演,得出应用形变资料联合反演压力源参数的公式,再指出用等效源半径反演时不同初始值对反演结果的影响,说明选择合适的初始值可以方便地得到可靠的反演结果。然后用此方法反演长白山天池火山区压力源的大小和位置参数。采用垂直和水平位移的联合反演,数据为2002—2005年共4期的水准和GPS观测资料,最后结合其它观测资料,分析近年来岩浆可能的活动特征。结果显示岩浆的位置在发生变化,体积增量逐年减小,表明火山岩浆在2002—2005年的活动逐年减弱     

腾冲火山地震群的活动特征

根据 1998 ,1999和 2 0 0 2年腾冲火山区流动数字地震台网的 3期观测资料 ,从中选择出 30个与岩浆活动有关的地震事件 ,这些事件主要以地震群的形式出现。从地震群的时空强分布特征、各观测台的地震波记录特征、震源参数和震源机制等方面 ,分析研究区内火山地震群的活动与岩浆囊体位置的关系。结果表明 ,腾冲火山区存在 2个岩浆囊体 ,一个位于北纬 2 5 0°～ 2 5 1° ,东经 98 4 2°～98 4 8° ,深度约 4～ 6km ;另一个位于北纬 2 4 9°～ 2 5 0 5° ,东经 98 4 5°～ 98 5 5°,深度约 8～ 14km以下。地震群活动主要围绕在岩浆囊体的周围 ,与岩浆活动密切相关。岩浆囊体的存在主要控制了腾冲南部火山区的地热活动及微小构造破裂     

用形变资料分析腾冲火山区岩浆的活动特征

联合1998~2004年的五期水准测量资料以及2002~2004年的GPS观测成果,分析了腾冲火山区岩浆的活动特征。垂直形变资料显示,火山区南部发生较明显下降,这可能是由岩浆和水的流失及放气等原因引起;水平形变资料显示,以固东—腾冲断裂(F2)的西支为界,断层两盘分别向东、西两个方向运动,断层活动表现出明显的拉张特征;综合分析表明,岩浆可能沿断层从南部向北部运移,并在断层内重新聚集形成岩墙;垂直形变的多个极值区以及水平位移的不规则性表明,火山区岩浆体不很规则或有多个岩浆囊体存在;从形变量大小分析,岩浆的活动量远小于中等程度火山喷发的质量,表明火山近期喷发的危险性较小。     

中国大陆火山监测研究进展

在过去几年里，长白山天池火山观测到了明显的地震活动增加、地表抬升和膨胀以及多种流体化学异常。地震学研究和形变模拟表明，长白山天池火山近年来的活动可能是由其下方的岩浆活动引起的。1993年以来，腾冲火山出现强烈的水热活动。地球化学参数的变化表明，气体源区的深度逐渐增加。火山区存在的震群活动、部分台站观测到的S波阴影区以及地表的缓慢抬升等，指示火山区存在一个岩浆系统。监测研究结果表明，目前我国大陆其他火山的活动性较弱。     

Recent Geochemical Variation of the Hot-Spring Gases from the Tianchi Volcano, Changbai Mountains, Northeast China

Recent fluid monitoring work shows that the contents of mantle-derived CO_2,He and CH_4 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 Changbaijulong 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.     

北天山泥火山对2012年6月30日 新源-和静MS6.6地震的响应

2012年6月30日新源-和静M_S6.6地震前后, 北天山泥火山出现了喷溢和地球化学异常变化. 该地震前、 后4天内两次观测了北天山泥火山, 采集了两批温泉和泥火山气体样品, 测定了样品的气体组分和He、 Ne同位素及CH₄、 CO₂的碳同位素组成. 结果表明, 泥火山发生了同震喷发, 气体排放量增加, 温泉和泥火山气体出现了不同程度的微量气体浓度异常, 独山子泥火山震前出现了3He/4He高值异常. 研究结果有利于确定利用泥火山和温泉监测地震活动的方法和指标.      

Aqueous fluids derived from a subducting slab: Observed high 3He emanation and conductive anomaly in a non-volcanic region,Kii Peninsula southwest Japan

It has long been recognized that the Kii Peninsula in the southwest Japan arc is peculiar in a non-volcanic region, indicated by the presence of high temperature hot springs, high terrestrial heat flow and high ³He content in hot spring gases. Geophysical and geochemical studies were carried out to understand the geotectonic environment in the southern part of the Kii Peninsula. Most of the measured ³He / ⁴He ratios are similar or higher than air, indicating wide spread incorporation of mantle-derived helium into meteoric water. A region with rather high ³He / ⁴He ratios (> 4 R_A) on the west side of the Omine Mountains coincides with the occurrence of high temperature hot springs. A deep crustal resistivity structure across the Omine Mountains was imaged by wide-band magnetotelluric soundings. A 2-D inversion with N–S strike using both TM and TE modes reveals two conductors, one in the upper (3–7 km depth) and the other in lower crust (25–35 km depth) to the west of the Omine Mountains. The distribution of microearthquakes and low-frequency tremors, and the existence of seismic reflectors indicate that the large conductor in the lower crust is related to aqueous fluids derived from the Philippine Sea plate. The upper-crustal conductive zone may also reflect the aqueous fluids trapped in the upper crust, which are presumably derived from the subducting slab. Considering the occurrence of seismic events in the subducting slab beneath the southern Kii Peninsula, the aqueous fluids generated by dehydration of the slab mantle could plausibly include MORB-type helium derived from the residual lithospheric mantle. Therefore, the high temperature hot springs and high ³He emanations in hot spring gases and other geotectonic events in the southern Kii Peninsula may be due to heat flux and mantle-derived helium discharged from aqueous fluid in the upper crust.     

Seismic wave attenuation in the upper Mantle beneath the Aegean region

A detailed study of P and S waves from earthquakes located along the Hellenic arc and recorded by the Greek seismological network, shows an abnormal distribution of the seismic waves in the central Aegean Sea. The data indicate a zone of anomalously high seismic wave attenuation in the Upper Mantle beneath the Cyclades plateau and the inner part of the volcanic arc. Several independent observations suggest the presence of magma beneath the Cyclades massif.In addition, geophysical data indicate the presence of low-density and rigidity material. Theoretical consideration of the propagation of elastic waves corroborate the observed absence of shear waves.     

Seismicity pattern and thermal anomalies in the southern Baltic region before and during the Kaliningrad earthquakes of 2004

The seismic situation in the SE Baltic region that existed during the period 1990–2006, including the unexpectedly strong Kaliningrad earthquakes of 2004, is analyzed. The spatiotemporal variation of seismic events in the region is examined on the basis of a newly compiled catalog of tectonic earthquakes. The analysis revealed outbursts of seismic activity in 1995 and 2004, structurization of the distribution of shocks, and their southward migration. The distribution of hot springs that arose in 2002–2004 is analyzed in relation to seismological data. The seismic process and thermal anomalies are shown to be geodynamically controlled, which provided constraints on the nucleation process and focal mechanism of the Kaliningrad earthquakes. The region, located in the western East European platform, should be regarded as seismically rather active.     

Multi-stage volcanism in the Ulleung Back-arc Basin, East Sea (Sea of Japan)

Abstract Multichannel seismic reflection profiling in the Ulleung back-arc Basin reveals that the acoustic basement largely comprises volcanic materials. The volcanics are interlayered with sediment sequences, forming an anomalously thick layer. The volcanic activities resulted in a zonation of the acoustic basement, trending northeast-southwest. In the southeastern part, the acoustic basement is deep and obscure, whereas in the northwestern part it is shallow and forms mounds and seamounts. The volcanic activities were probably initiated in the Early Miocene ( ca 20Ma). The volcanism was time-transgressive northward, associated with the possible southward drift of the Japanese islands.     

温泉逸出气体常规成分快速测定

通过对腾冲火山地球化学观测站中用气相色谱仪对火山区温泉逸出气体成分的观测实践的理论总结,系统介绍了用气相色谱仪对温泉逸出气体常规成分的快速测定方法.结果表明,SP3400型气相色谱仪具有一系列优点.通过合理的仪器配置、参数设置、规范的运行维护和分析操作,SP3400型气相色谱仪可以快速准确地分析温泉逸出气体中He、H_2、O_2、N_2、CH_4、CO_2等常规组分的含量.对这些组份总量分析的相对偏差只有1.89%,对CO_2组份分析的相对偏差只有2.18%,对He、H_2等ppm级含量的组份分析的相对偏差分别只有10.24%和11.44%,说明SP3400的型气相色谱仪的测试结果有相当高的可靠性和准确性.SP3400型气相色谱仪为温泉逸出气体常规组分快速测定的理想仪器,可以在火山和地震监测台站推广使用.     

黑龙江五大连池火山区气体地球化学特征

根据五大连池火山区的气体地球化学特征,分析了二氧化碳气的生成条件和成因,对火山区CO_2的泄出量进行了概算。通过一年定点观测,查明了南泉和二龙眼泉各气体组分的动态变化特征,认为南泉氢和氦于1988年2月～4月出现的大幅度异常和附近的小震活动有关