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1.
2002年8月20日长白山天池火山小震震群研究 总被引：17，自引：2，他引：17
2002年7～9月，采用15台宽频带流动地震仪在长白山天池火山区进行了近3个月的地震观测，记录到大量发生在天池火山附近的地震和多次小震群。对2002年8月20日的小震群进行了分析，结果表明这些地震发生在长白山天池内的西南部，震源深度距离天池水面一般小于4km深，震群的震中位置呈北西向线性分布。地震记录的频谱分析表明，该震群为典型的火山构造类型地震。在观测中发现HSZ和DZD台的地震记录低频成份丰富，这可能与台站附近的局部介质变化或低速的断层带有关。我们认为震群可能是由火山深部活动诱发的局部断裂活动所引起。 相似文献
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长白山天池火山区的谐频事件 总被引：2，自引：0，他引：2
通过对长白山天池火山地区2002、2003和2005年夏季3期流动地震观测资料的频谱分析,发现火山口附近存在一种在频率域中形态比较特殊的地震事件,其频谱由1组等间隔的谱峰构成,峰值振幅随频率缓慢变化,形态与时间域中的谐波信号相似,我们把这种地震事件称为谐频事件。在3个夏季的流动观测中,共发现38个谐频事件,且这些事件大多与震群活动有关。分析表明,谐频地震频谱中的谐波现象与震源有关,可能是岩石破裂过程中,在特殊激发条件下,裂缝壁和裂缝内部岩浆或热液的压力扰动相互作用产生的。我们认为近年来长白山天池地震活动的突然增加和谐频事件的出现与深部岩浆的侵入活动有关 相似文献
3.
用双差地震定位法对2005年9月23日克孜尔震群进行重新定位。 从平面上, 重新定位地震集中分布在一个长约14.5 km, 宽约 9.0 km的长方形内, 其长轴为N30°W向, 与克孜尔断裂近乎垂直。 从震源深度来看, 重新定位地震的震源深度全部分布在21 km以内, 集中分布在10~19 km, 平均深度为13.6 km; 震群中绝大部分小震发生在沉积层内, 而震级较大地震基本发生在结晶地壳的上地壳内。 其剖面图显示, 这次震群是从结晶地壳开始沿着N30°W方向向上破裂至沉积层。 根据震区附近断裂性质和该区历史小震震中分布分析认为, 克孜尔水库库区附近可能存在两条共轭断裂, 右翼断裂可能是这次震群的发震构造。 相似文献
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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. 相似文献
5.
长白山天池火山地震类型及火山活动性的初步研究 总被引：3，自引：0，他引：3
2002年以来，长白山天池火山区出现了地震活动增强、地形变加剧和多种地球化学异常等现象，火山口附近发生的多次有感地震在社会上产生了较大影响。本文利用2002年以来的流动地震观测资料，采用频谱分析、时频分析和多台站资料对比的方法，对火山区地震事件的类型进行了分析；对火山活动的危险性进行了初步研究。结果表明，目前天池火山区出现的大量地震活动仍然属于火山构造地震，少量台站地震记录中表现出的低频特征主要是由于局部介质影响造成的，排除了长周期地震引起的可能。尽管长白山天池火山地震活动明最增强，震群活动较为频繁，但仍属于岩浆活动的早期阶段，短期内发生火山喷发的危险性较小。 相似文献
6.
福建仙游地区自2010年8月开始出现地震序列活动,2012年地震活动水平有所提高,2013年以来地震活动水平进一步提高,ML3.0以上地震集中活跃。福建数字化地震台网对这些地震进行了较完整的监测,记录到丰富的观测资料。通过利用P、S波到时数据对ML≥1.0地震序列进行重新定位,发现地震序列空间位置和震源深度呈现出不同的时段性分布特征。同时利用福建数字化地震台网记录到的波形资料,采用"剪切-粘贴"法,获取了ML≥3.5的震源机制解和最佳震源深度。通过震群序列活动特征、震源位置分布、震源区断层活动分布以及震源机制解特征综合判断认为:仙游震群序列为库水下渗促使断裂滑动引起的构造地震,属于水库诱发型构造型地震,发震构造为穿过库区的NW向石苍断裂。 相似文献
7.
本文使用双差定位法对2014年9月12日至12月30日浙江珊溪水库发生的4184次地震进行重定位，并采用CAP方法对11次ML≥3.0地震事件的震源机制解进行反演，讨论了震群序列的活动特征及其与断裂之间的关系，分析了水库水位与地震之间的关系.重新定位的结果显示，在空间分布上，2014年震群序列发生在2006年震群序列NW向延伸的方向上，两者形成一条线性条带，该条带平行分布于双溪—焦溪垟断裂南侧.重定位得到的震源主要在0.7—6 km深度范围内分层分布，垂直于地震条带走向的震源剖面刻画出的结构面以高角度倾向SW.震源机制解结果显示多数地震为走滑型，均存在一个与地震条带走向一致的NW向节面，呈右旋走滑错动性质.考虑到断裂的定位误差，线性分布的震群活动极有可能沿双溪—焦溪垟断裂的破裂面活动，精定位的震源位置和震源机制刻画出了该断裂的几何结构和活动性质.但由于多数地震的震源深度在6 km以上，因此震群活动不能归为双溪—焦溪垟断裂活动的结果，即双溪—焦溪垟断裂不是这两次震群的发震构造，而且仍然属于水库诱发地震，而水库地震存在激发该断裂发生构造地震的可能.水库水位上升或者下降与震群活动关系不大，震群活动有随时间进一步增强的趋势, 可能是库水沿库底断层破裂面长期渗透和扩散增加了孔隙压所致. 相似文献
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《地球物理学进展》2017,(3)
本文利用自适应量子遗传算法对山东胶东半岛乳山地区2013年10月至2015年9月年发生的1357次显著震群活动进行了重定位研究.自适应量子遗传算法具有效率高、搜索能力强等优点,利用自适应量子遗传算法进行地震重定位后大大改善了原地震定位的精度,研究结果表明均方根残差由重定位前的0.40 s减小到重定位后的0.22 s.重定位后的地震震中更集中,条带状更为清晰,总体呈NW向分布.震源深度主要集中在2~16 km范围内的中上地壳,占地震总数的95.8%.乳山震群的最大震源深度为23 km,推测该区地震活动的下界为23km,与华北地区脆韧性转化带相一致.综合乳山震群精定位结果、震群ML3.0级以上地震的震源机制解与区域构造特征,推测其发震构造为NW向近直立隐伏断层. 相似文献
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根据2016年运城4.4级地震序列资料，进行余震精定位、主震震源机制和发震构造等研究。地震震中分布结果显示，本次地震的发生构造与以往该地区震群型地震发震构造不同，构造单元相对简单，发生在盐湖北岸断裂附近。余震双差精定位结果显示，余震优势分布呈NNE向，NW向也有零星活动。精定位后震源深度集中分布在15-24 km，平均深度20.2 km，断层剖面深度集中分布在18-23 km，倾向NW，与盆地地形构造吻合。采用Snoke与CAP方法得到的震源机制解基本一致，此次序列的主震错断方式为走滑兼逆冲，节面B参数与中条山山前断裂东段走向和倾向接近。综合认为，本次运城地震序列的余震呈NNE向优势分布，精定位结合地震震源机制结果，推断此次地震序列发震断裂为中条山山前断裂的NNE向隐伏断裂。 相似文献
11.
A Preliminary Study of the Types of Volcanic Earthquakes and Volcanic Activity at the Changbaishan Tianchi Volcano 总被引：1，自引：0，他引：1
Ming Yuehong 《中国地震研究》2006,20(3):286-294
INTRODUCTIONThe Changbaishan volcano is located in Jilin Province , along the border of China and NorthKorea .It isthelargest nature reservein China .Changbaishan belongstothe northeastern Asian activebelt in the eastern margin of the Euro-Asia plate . The Changbaishan volcano is a gigantic ,polygenetic ,central volcano,and has been active since Holocene .The early eruption started in thePliocene andformedthe basaltic shield. Duringthe middle and late Pleistocene ,the volcanic cone … 相似文献
12.
Attenuation of Coda Waves at the Changbaishan Tianchi Volcanic Area in Northeast China 总被引：2，自引：0，他引：2
21 earthquakes recorded by a temporary seismic network in the Changbaishan Tianchi volcanic area in Northeast China operated
during the summer of 2002 and 2003 were analyzed to estimate the S coda attenuation. The attenuation quality factor Qc was estimated using the single scattering attenuation model of Sato (1977) in the frequency band from 4 to 24 Hz. All the
events studied in this paper occurred at depths from 2 to 6 km with ML of 1.4–2.8. The epicentral distances are less than
25 km. For all events which occurred near the Tianchi Lake (caldera), the Qc patterns obtained at the stations near the lake are similar, and the Qc values are relatively small. At the stations located about 15 km east of the Tianchi Lake, however, the average Qc is significantly higher. For an event which occurred 25km from the lake to the west, Qc patterns derived at the stations near the lake are quite similar to the above mentioned Qc for stations located in the east. Further study shows that Qc value in the north and central areas of the volcano is relatively lower than that in the surrounding area. Compared to other
volcanic areas in the world, the average Qc of the Changbaishan Tianchi volcanic area is obviously lower. The deep seismic sounding and teleseismic receiver function
studies indicated more than one lower velocity layer in the crust. The MT studies suggested the presence of high conductive
bodies beneath the area. We interpret the strong attenuation of coda waves near the Changbaishan Tianchi volcano as being
possibly related to high temperature medium caused by shallow magma chambers. 相似文献
13.
The first sign of magma accumulating beneath Miyakejima, an island volcano in the northern Izu islands, Japan, came at around 18:00 on 26 June 2000, when a swarm of earthquakes was detected by a volcano seismic network on the island. Earthquakes occurred initially beneath the southwest flank near the summit and gradually migrated west of the island, where a submarine eruption occurred the next morning. Earthquakes then migrated further to the northwest between Miyakejima and Kozushima, another volcanic island and developed to the most intense earthquake swarm ever observed in and around Japanese archipelago. To better image how the initial magma intrusion occurred, we relocated hypocenters by using a station-correction method and a double-difference method. The relocated epicenters are generally concentrated near the upper bound of dyke intrusions inferred from geodetic studies throughout the initial stages of the 2000 eruption at Miyakejima from 26 to 27 June 2000. As for seismic activity westward off Miyakejima in the morning on 27 June, hypocenters from both a nationwide seismic network that were relocated by the double-difference method, and those from the volcano seismic network relocated by the station-correction method, formed a very shallow cluster that ascended slowly with time as it propagated northwestward from Miyakejima. This suggests that the dykes have both a radial and upward component of movement.Editorial responsibility: S. Nakada, T. Druitt 相似文献
14.
A major seismic swarm occurred near Parícutin volcano between the end of May and early July 2006. More than 700 earthquakes
with magnitude (M
L
) exceeding 2.4 were located. Parícutin, located in the Michoacán–Guanajuato volcanic field in western Mexico, is well known
as the site of the 1943 eruption in which a new 400 m cinder cone was constructed in what had been farmland. The 2006 swarm
exhibits all of the characteristics typically associated with swarms of volcanic origins. The earthquake rate showed the typical
ramp up and ramp down over the course of several days. Magnitudes were evenly distributed in time with a notably high b-value
of 2.45. The earthquake locations cluster around a northeast-striking trend extending approximately 6 km. Over the first two
weeks, hypocenters migrated steadily a few hundred meters per day, rising from 9 to 5 km depth and moving northeast about
5 km. On approximately June 7, the ascent of hypocenters stalled. For the next three weeks, hypocenters held their depth while
migrating laterally back to the southwest. Focal mechanisms during the first part of the swarm reflected the increased stress
caused by dike inflation. Following June 7, the stress orientation changed and became more consistent with the inflation of
horizontal sill-like structures. Though only limited information is available from the seismic swarm preceding the 1943 eruption,
several features, including the swarm duration and magnitude relationships, were comparable to those of the 2006 episode.
The strong indicators of a magmatic origin to the 2006 swarm suggest that at this location there are few, if any, traditional
seismic discriminants that could be used to distinguish which seismic swarms and dike emplacement events might culminate in
eruption. 相似文献
15.
中国大陆火山监测研究进展 总被引：4，自引：2，他引：4
吴建平 《地震地磁观测与研究》2005,26(5):1-10
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。 相似文献
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Jianping Wu Yuehong Ming Lihua Fang Weilai Wang Institute of Geophysics China Earthquake Administration Beijing China 《地震学报(英文版)》2009,(4):409-416
The S wave velocity structure in Changbaishan volcanic region was obtained from teleseismic receiver func-tion modeling. The results show that there exist distinct low velocity layers in crust in volcano area. Beneath WQD station near to the Tianchi caldera the low velocity layer at 8 km depth is 20 km thick with the lowest S-wave velocity about 2.2 km/s. At EDO station located 50 km north of Tianchi caldera,no obvious crustal low velocity layer is detected. In the volcanic re-gion,the thickness of crustal ... 相似文献