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1.
Mechanical response of the south flank of kilauea volcano, hawaii, to intrusive events along the rift systems 总被引：1，自引：0，他引：1
John J. Dvorak Arnold T. Okamura Thomas T. English Robert Y. Koyanagi Jennifer S. Nakata Maurice K. Sako Wilfred T. Tanigawa Kenneth M. Yamashita 《Tectonophysics》1986,124(3-4)
Increased earthquake activity and compression of the south flank of Kilauea volcano, Hawaii, have been recognized by previous investigators to accompany rift intrusions. We further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major rift intrusions which occurred between December 1971 and January 1981. The seismic response of the south flank to individual rift intrusions is immediate; the increased rate of earthquake activity lasts from 1 to 4 weeks. Horizontal strain measurements indicate that compression of the south flank usually accompanies rift intrusions and eruptions. Emplacement of an intrusion at a depth greater than about 4 km, such as the June 1982 southwest rift intrusion, however, results in a slight extension of the subaerial portion of the south flank.Horizontal strain measurements along the south flank are used to locate the January 1983 east-rift intrusion, which resulted in eruptive activity. The intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet. This model suggests that the intrusive body that compressed the south flank in January 1983 extended from the surface to about 2.4 km depth, and was aligned along a strike of N66°E. The intrusion is approximately 11 km in length, extended beyond the January 1983 eruptive fissures, which are 8 km in length and is contained within the 14-km-long region of shallow rift earthquakes. 相似文献
2.
C.D. Lindholm H. Bungum R.K. Bratli B.S. Aadnøy N. Dahl B. Tørudbakken K. Atakan 《地学学报》1995,7(1):51-59
The regional stress field in the northern North Sea (offshore western Norway) has been studied through the acquisition and analysis of directions of maximum horizontal compression (H ) as extracted from borehole breakouts and from earthquake focal mechanism solutions.
The results indicate that the regional stress field is dominated by NW-SE compression, with good consistency between shallow borehole breakouts (2–5 km depth) and deeper earthquakes (10–25 km depth). The broad spatial consistency in stress direction indicates that the main stress field is related to factors of primarily plate tectonic origin, and the results are in good agreement with the western Europe trend found in earlier investigations.
The Tampen Spur region in the northern North Sea has been subjected to particularly complex deformation, with two dominating fault directions trending NW-SE and NE-SW. From Tampen Spur in the west to the Sogn graben in the east an anomalous stress field is indicated, with NE-SW oriented maximum horizontal compressions. This anomaly is clearly seen both in the borehole breakout data and in the earthquake data. Possible sources for this anomaly are discussed, and include postglacial uplift and/or lateral variations in the physical properties of the crust. 相似文献
The results indicate that the regional stress field is dominated by NW-SE compression, with good consistency between shallow borehole breakouts (2–5 km depth) and deeper earthquakes (10–25 km depth). The broad spatial consistency in stress direction indicates that the main stress field is related to factors of primarily plate tectonic origin, and the results are in good agreement with the western Europe trend found in earlier investigations.
The Tampen Spur region in the northern North Sea has been subjected to particularly complex deformation, with two dominating fault directions trending NW-SE and NE-SW. From Tampen Spur in the west to the Sogn graben in the east an anomalous stress field is indicated, with NE-SW oriented maximum horizontal compressions. This anomaly is clearly seen both in the borehole breakout data and in the earthquake data. Possible sources for this anomaly are discussed, and include postglacial uplift and/or lateral variations in the physical properties of the crust. 相似文献
3.
The Yaojiachezhan (YJCZ) section and NGN1, Zk3389 and SK1-S wells, which are located in the southeastern part of the Songliao Basin, NE China, were used to analyse paleoseismic events recorded in the Upper Cretaceous first member of the Nenjiang Formation. Two representative seismic sequences are recognised in these lacustrine deposits. The seismic sequence observed in the YJCZ section, from the base to top, includes step micro-faulting, seismic fissures, liquefaction sandstone veins, brecelated structures, liquefied fold-deformed laminations and sand pillow structures. Whereas in NGN1 core, from the base to top, includes micro-faulting, seismic fissures, sand pillow structures, liquefied fold-deformed laminations and liquefaction sandstone veins. These two seismic sequences together reflect the processes resulting from a strong seismic event from initiation to culmination, then decline and recession. The occurrence of brecciated structures reflects the earthquake magnitude in the YJCZ section area probably reached M7.5, while liquefied fold-deformed laminations in the NGN1 core area reflects an earthquake magnitude of M7.0. Empirical relations between earthquake magnitude and the maximum distance of liquefaction deformation structure sites from the epicentres show that the longest distance between the earthquake source area for the YJCZ section and NGN1 well are <100?km, whereas the distance for the Zk3389 and SK1-S wells is >100?km. The trigger source area for this paleoseismic event is most likely the Yilan-Yitong Fault, meaning that the Yilan-Yitong Fault was active during the deposition of the first member of the Nenjiang Formation. 相似文献
4.
Mehdi A. Guemache Djamel Machane Hamoud Beldjoudi Sofiane Gharbi Leila Djadia Sihem Benahmed Hayet Ymmel 《Natural Hazards》2010,54(2):273-288
On March 20, 2006, an earthquake (M
w = 5.3; SED) struck the mountainous region of the Babors chain (Wilaya of Bejaia, northeast Algeria). The seismic epicenter
was located near the Kherrata village. This earthquake was felt on a large area of the northeastern part of Algeria. It reached
an intensity of VII (EMS scale) at the Laalam village, situated at about 20 km northeast of Kherrata. Here, many old and recent
houses were damaged or collapsed totally, four people died and 68 were injured. Field investigations revealed that these casualties
were caused by a landslide triggered by the earthquake. Many fissures were visible on ground throughout the site. They were
generated by both sliding and settling phenomena. The Laalam site is prone to landslide, as revealed by some evidences on
old instabilities. This is due to two main factors: local geomorphology and geology. These factors intervene synchronously
for reducing the slope instability at the Laalam village. The March 20, 2006 Kherrata earthquake was the trigger that released
the Laalam landslide. 相似文献
5.
贵州地震时空分布规律探析 总被引：1，自引：1，他引：0
如果以垭都—紫云—罗甸断裂带北东侧为界将贵州省分为A、B两个区域,则：①地震在A区分布较为密集,而在B区分布较为稀散。单位国土面积上释放的地震能量,前者比后者要大一个数量级,反映两者在力学性质上存在较大差异。②A区地震释放能量在深度约5.5km处突然出现一个高达2个数量级的跃升,在深度约7 km处回落到接近跃升前的位置,而后又逐渐下降,反映该区域5.5～7 km深度地层的力学强度较低。③贵州地震释放能量总体似乎呈周期性变化,变化周期在11～15年间变动。A、B两区域地震释放能量的高峰年有此消彼长的现象,即A区出现地震活动高峰时,B区相对比较平静;而B区出现地震活动高峰时,A区相对比较平静。 相似文献
6.
The epicentre of the Roermond earthquake is located near the western boundary fault of the Roer valley trough, one of the deepest and the most active in the Quaternary part of the Lower Rhine graben. The Late Pleistocene and Holocene activity of the trough is manifested by offsets of the main (Mindel) and the lower (Riss and Late Pleistocene) terraces along the boundary faults.
Surface fractures have been observed in an area of more than 50 km2 : 2.5–3.5 km to the north of the town of Roermond, at 0.8 km to the south of the village of Herkenbosch and in the southeastern part of the village of Montfort. Three types of ruptures were differentiated: scarps up to 50 cm high along open fractures near the Maas River; open fractures (continued by scarps in some places) and open fractures with a liquefaction of the Quaternary alluvium sands. The last type is predominant. The location of the ruptures depends on the landscape and water-table of the region. While they could be produced solely by hydraulic shock during the earthquake (increased by the wet spring season), the majority of the ruptures strike N50°W ± 10°, i.e. parallel to the main trough faults, or N55°E ± 10°, along 'neotectonic lines', parallel to the Maas valley and deduced from space imagery. Thus, the ruptures could be the secondary surficial effect of the earthquake, linked indirectly with the active tectonics of the region. 相似文献
Surface fractures have been observed in an area of more than 50 km
7.
四川芦山2013年Ms7.0地震发震构造初步研究 总被引：3，自引：0，他引：3
2013年4月20日8时2分,四川龙门山断裂带的雅安芦山发生Ms7.0级地震,震中位于芦山县太平镇和双石镇之间,震源深度13～14km,震中最大烈度达IX级。震中区野外调查发现,尽管房屋建筑损坏较严重,但这次地震没有产生明显的地表破裂构造,仅见少量的地裂缝和喷砂冒水现象。高分辨率遥感图像解译、主余震分布、震源机制解等综合分析认为,该地震是龙门山断裂带西南段一次独立的破裂事件,属于逆冲型地震,沿双石-大川断裂中南段发生破裂,主破裂面西倾,倾角33°～43°,推断芦山地震与龙门山构造带底部滑脱带(13～19km)断坡构造活动有关。历史上,沿双石-大川断裂发生至少2次Ms6～6.5级地震,由此认为芦山地震是龙门山断裂带西南段特征型地震,与汶川地震不同。原地地应力测量和监测数据表明这是汶川地震后龙门山断裂带西南段应力释放的结果。 相似文献
8.
地裂缝及其灾害研究的新进展 总被引：31，自引：0，他引：31
已查明我国 2 6个省市出现具一定规模的地裂缝 1 0 0 3处 ,60 0 0多条。其中 80 %是构造地裂缝 ,它们是地壳浅表层破裂。区域地裂缝与强震区分布一致 ,活跃期也相吻合 ,它们是同一构造应力场作用的不同构造现象 ,区域地裂缝释放地壳应变能远超过同期强震能量释放的总和。作为动力源的地裂缝活动使同期地质体发生位移产生形变场和应力场 ,并通过地基使建筑物结构等失稳失效破坏成灾 ,估算全国地裂缝造成的损失为 91 .2亿元 ,其中华北区损失占 70 %。地裂缝已构成一个新的独立的灾种。 相似文献
9.
M. Meghraoui 《地学学报》1991,3(1):84-92
A shallow and damaging earthquake struck the region of Tipaza located on the coast, 70 km to the west of Algiers (north-central Algeria). The main shock was felt as far as 200 km from the epicentral area and particularly in the urbanized zone of Algiers. The main shock epicentre determined by CRAAG is on Mt Chenoua, close to the coastline. Coseismic surface breaks with 4.0 km of fault length and 7.0 cm of vertical displacement appeared on the southern side of Mt Chenoua. They consist of cracks and fissures on vertical bedding planes that belong to a Neogene flexure. The aftershock activity was recorded for several weeks and comprised more than 100 seismic events per day, with 1 < M < 5. Aftershocks are distributed in a ENE-WSW to NE-SW zone extending offshore. A NW-SE cross-section indicates that seismic events affect the crust to a maximum depth of 20 km, showing a complex fault-plane geometry dipping to the NW. For the main shock, the focal mechanism solution obtained from the readings of first motion polarities of seismograms yields an ENE-WSW reverse fault dipping to the NNW, which is in good agreement with both field observations and the aftershock distribution at depth.
The occurrence of the Mt Chenoua-Tipaza moderate-sized event in a previously identified active zone improves the seismotectonic characterization of this part of the Tellan Atlas mountains. This thrust and fold geological domain also shows active folds capable of producing larger earthquakes. Since only a small portion of the Sahel anticline ridge has been reactivated, a serious seismic hazard must be urgently recognized in the Algiers region. 相似文献
The occurrence of the Mt Chenoua-Tipaza moderate-sized event in a previously identified active zone improves the seismotectonic characterization of this part of the Tellan Atlas mountains. This thrust and fold geological domain also shows active folds capable of producing larger earthquakes. Since only a small portion of the Sahel anticline ridge has been reactivated, a serious seismic hazard must be urgently recognized in the Algiers region. 相似文献
10.
Earthquake swarms of Mt Cameroon, West Africa 总被引：1，自引：0，他引：1
Richard U. Ubangoh Bekoa Ateba Samuel N. Ayonghe G.E. Ekodeck 《Journal of African Earth Sciences》1997,24(4):413-424
Historical and recent instrumental studies of the central region of the Cameroon Volcanic Line clearly indicate the occurrence of earthquake swarms of volcanic origin. Analyses of more than 3000 micro-earthquakes recorded between 1985 and 1992 show a well-defined seismic pattern characterised by single and swarm events with duration magnitudes between 2 and 3 at depths down to 20 km. On average, the earthquakes here occur at the rate of about 2 events every 3 days with occasional earthquake swarms, which greatly increase this number. The seismic swarms comprising felt earthquakes are shown to be sometimes preceded by, simultaneous with, or followed by swarms from Bimbia and Equatorial Guinea. Mapped epicentres of some of these swarms correspond to regions of volcanic gas emissions and are parallel to the fissures on Mt Cameroon and to the inferred direction of the underlying shear zone.The quiescent periods between swarms are seen to double each year since 1986. This observation was used to predict a major seismic swarm which occurred in 1993. The data coupled with historical data, are used to infer the involvement of a magma chamber in the generation of the earthquake swarms in the region. Since the installation of the network, no eruption has been observed on Mt Cameroon. This warrants more observation in order to study the seismicity that may precede, accompany or follow an eruption of the mountain. 相似文献
11.
芦山地震发震构造及其与汶川地震关系讨论 总被引：14，自引：0，他引：14
芦山地震发生在巴彦喀拉块体与华南块体之间龙门山推覆构造带南段。野外考察表明,芦山地震在震中区没有形成具有构造地质意义的地震地表破裂带,仅在各山前陡坡地带出现平行于山麓陡坡的张性地裂缝、山地基岩崩塌、滑坡等边坡震动失稳现象和震动引起的砂土液化现象。重新定位的芦山地震余震分布、震源机制解和地表构造地质等分析表明,芦山地震的发震断层为一条现今尚未出露地表、其上断点仍埋藏在地下9 km以下地壳中的一条盲逆断层,走向212°,倾向NW,倾角38°±2°,上断点以上至地表的构造变形符合断层扩展背斜模型。根据汶川地震和芦山地震的余震空间分布、地震破裂过程、深浅构造关系等差异反映出它们是分别发生在龙门山推覆构造带中段和南段的两次独立地震破裂事件。 相似文献
12.
M. K. Gupta 《Journal of Earth System Science》2003,112(3):347-352
The occurrence of a severe earthquake is a rare event with its effect localized in a limited region. There are no prior indications
of its occurrence too; hence experiencing such an event is just a matter of chance, which the author had by virtue of his
posting at Bhuj. This paper presents a detailed account of observations made in the wake of the Bhuj earthquake of January
26th 2001, describing physical and mental reactions during the earthquake, the post-quake scenario, the nature and cause of
damage to buildings, the trend of aftershocks, various deformities, including ruptures and fissures on the surface of the
earth, etc. which may be useful for a detailed study of the seismological activity in the region. 相似文献
13.
深井水温观测在中国已经开展了20多年,但目前对于水温响应机理的研究还不充分.而且利用温泉水对水温响应机理研究甚少.本文在2008年5月12日汶川8.0级地震前后,即2008年5月1日至7月4日,对重庆北温泉水(距震中约400 km)进行采样监测,发现泉水水温水量发生较大变化:震后水温下降了1℃:海拔相对较高的BWQ-2、BWQ-3、BWQ-4相继断流,监测点BWQ-1的水量增加了15 L/s;与此同时.各泉点Fe~(3+)、Mn~(2+)浓度于地震当日成倍增长,随后逐渐减小,7月4日时浓度与5月1日相当.重庆北温泉位于四川盆地东部边缘地带,受汶川地震强烈影响导致冷水下渗作用,海拔相对较高而温度较低的温泉水改道,并有其他来自裂隙或者地表的低温水汇入温泉含水层,Fe~(3+)、Mn~(2+)浓度的变化从水化学上印证了冷水下渗学说. 相似文献
14.
张秦华 《地质灾害与环境保护》2016,(3):30-34
泾阳县北部地区是地裂缝灾害发育的地区,地裂缝主要分布在山前冲洪积扇区,发育在全新世地层中,平面形态上为直线型、雁列型、锯齿型和弯曲形,在分布上有方向性和群集性,在范围上从北到南呈逐渐扩大的趋势。本文在对区内地质环境论述的基础上,总结了区内地裂缝的发育特征和分布特征,分析了该区地裂缝的形成条件。作者认为其主要影响因素为土体结构、地质构造、地震、降雨和灌溉入渗。 相似文献
15.
2016年11月25日新疆阿克陶县木吉乡发生MS6.7地震,发震构造为公格尔山拉张系北端的木吉断裂,断裂总长度超过100 km,以右旋走滑为主兼有一定的拉张分量。文章在对震区进行了初步的地震地质灾害调查,总结砂土液化和地裂缝在高原季节性冻土地区的分布及发育特点的基础上,发现:1)在研究区Ⅰ维日麻村的砂土液化主要沿原有泉眼或沿地裂缝发育,沿泉眼形成的砂土液化其喷砂锥的覆盖面积达36.1 m2,占总液化面积的60%,研究区Ⅱ布拉克村的砂土液化则主要是沿草甸的根系喷出,在地表形成大面积的最新涌水结冻特征;2)对研究区Ⅱ布拉克村地裂缝的深度进行统计,反演出区域冻土层厚度,结合探槽揭露的地层剖面,推断冻土层发生大面积地裂缝是因为地震引起冻土层下部融土层发生砂土液化导致土层变形失稳,从而使冻土层发生形变产生一系列规律性的地裂缝。 相似文献
16.
In estimating the likelihood of an earthquake hazard for a seismically active region, information on the geometry of the potential
source is important in quantifying the seismic hazard. The damage from an earthquake varies spatially and is governed by the
fault geometry and lithology. As earthquake damage is amplified by guided seismic waves along fault zones, it is important
to delineate the disposition of the fault zones by precisely determined hypocentral parameters. We used the double difference
(DD) algorithm to relocate earthquakes in the Koyna-Warna seismic zone (KWSZ) region, with the P- and S-wave catalog data
from relative arrival time pairs constituting the input. A significant improvement in the hypocentral estimates was achieved,
with the epicentral errors <30 m and focal depth errors <75 m i.e. errors have been significantly reduced by an order of magnitude
from the parameters determined by HYPO71. The earthquake activity defines three different fault segments. The seismogenic volume is shallower in the south by 3 km,
with seismicity in the north extending to a depth of 11 km while in the south the deepest seismicity observed is at a depth
of 8 km. By resolving the structure of seismicity in greater detail, we address the salient issues related to the seismotectonics
of this region. 相似文献
17.
Variations of seismic mode in the region of the Avachinsky Gulf (Kamchatka, Russia) are considered. Observed anomalies (seismic quiescence, the ring seismicity, reduction of the slope of the earthquake recurrence diagram) provide a basis to consider this region as a place of strong earthquake preparation. The Kamchatka regional catalogues of earthquakes between 1962–1995 were used in the analysis. A reduced seismicity rate is observed during 10 years in an area of 150 km × 60 km in size. During the last five years, in the vicinity of the area considered, earthquakes with M > 5 occurred three times more often than the average over thirty years. It is interpreted as ring seismicity. The block of 220 km × 220~km in size, including the quiescence zone, is characterized by a continuous decrease of the recurrence diagram slope, which has reached a minimum value for the last 33 years in this region. 相似文献
18.
EMERGEO Working Group 《地学学报》2010,22(1):43-51
An earthquake of Mw = 6.3 struck L'Aquila town (central Italy) on 6 April 2009 rupturing an ∼18-km-long SW-dipping normal fault. The aftershock area extended for a length of more than 35 km and included major aftershocks on 7 and 9 April and thousands of minor events. Surface faulting occurred along the SW-dipping Paganica fault with a continuous extent of ∼2.5 km. Ruptures consist of open cracks and vertical dislocations or warps (0.1m maximum throw) with an orientation of N130°–140°. Small triggered slip and shaking effects also took place along nearby synthetic and antithetic normal faults. The observed limited extent and small surface displacement of the Paganica ruptures with respect to the height of the fault scarps and vertical throws of palaeo-earthquakes along faults in the area put the faulting associated with the L'Aquila earthquake in perspective with respect to the maximum expected magnitude and the regional seismic hazard. 相似文献
19.
2008年5月12日14时28分04秒,四川省汶川县发生MS8.0大地震。发震断裂为龙门山断裂带,地震地表破裂带分布在北川-映秀断裂上的映秀-石坎子段和江油-灌县断裂上的磁峰-睢水段。平武县平通镇地表破裂现象典型,在T1和T2阶地上形成了地震断坎和裂缝。应用高精度GPSRTK技术对平通镇地震断坎及两侧作详细的地形测量,并测量了线性显著的路面中线和鱼塘西边壁。在室内生成高分辨率DEM与大比例尺地形剖面图,量取同震垂直与水平位移,并估算压缩缩短量和断层产状。结果显示汶川8.0级地震在平通镇形成的同震垂直位移为3.0±0.1m,右旋水平位移为4.0±0.2m,压缩缩短量为2.5m,断层产状为NE40°/NW∠50°。平通镇的同震右旋位移与本次地震的最大右旋位移相近,而逆冲垂直位移有所降低。 相似文献
20.
ZHANG Yueqiao DONG Shuwen HOU Chuntang SHI Jusong WU Zhonghai LI Hailong SUN Ping LIU Gang LI Jian 《《地质学报》英文版》2013,87(3):633-645
At 08:02 on April 20, 2013, a Ms7.0 earthquake occurred in Lushan, Ya'an, in the Longmenshan fault zone, Sichuan. The epicenter was located between Taiping Town and Shuangshi Town, Lushan County and the maximum earthquake intensity at the epicenter reached class IX. Field investigations in the epicenter area found that, although buildings were seriously damaged, no obvious surface rupture structure was produced, only some ground fissures and sand blows and water ejection phenomena being seen. An integrated analysis of high-resolution remote sensing image interpretation, mainshock and aftershock distribution, and focal mechanism solutions indicated that this earthquake was an independent rupturing event in the southwestern segment of the Longmenshan fault zone, belonging to the thrust-type earthquake. Ruptures occurred along the south-central segment of the Shuangshi-Dachuan fault and the principal rupture plane dipped SW at 33-43°. It is inferred that the Lushan earthquake might be related to the ramp activity of the basal detachment zone (13-19 km) of the Longmenshan fault zone. Historically, there occurred at least two Ms6-6.5 earthquakes along the Shuangshi-Dachuan fault zone; thus it is thought that the Lushan earthquake, different from the Wenchuan earthquake, was a characteristic one in the southwestern segment of the Longmenshan fault zone. In-situ stress measurements indicated the Lushan earthquake was the result of stress release of the southwestern segment of the Longmenshan fault zone after the Wenchuan earthquake. This paper analyzes the tectonic setting of the seismogenic structure of this earthquake. 相似文献