福建仙游震群重定位及序列特征分析

使用福建东南沿海地壳速度结构模型,利用双差定位方法(hypodd),对2010年8月—2013年12月福建仙游地区震群序列进行重新定位,讨论仙游震群序列的变化特征。定位结果显示,仙游震群序列主要围绕金钟水库蓄水区周缘活动,震源位置和深度表现出一定时空阶段性分布特征,并具有一定水库地震性质。     

福建仙游地震序列活动特征研究

自2010年8月以来,福建仙游地震序列持续地震活动,空间分布呈北西向线性展布。仙游序列地震活动具有明显的时空分段特征,时间上存在4个密集活动时段,空间上地震活动主体区域呈现出自北西向南东方向迁移特征。序列ML≥3.0级地震震源机制解结果多为走滑性质,其北西向节面解与区域内分布的沙县—南日岛断裂带走向一致,认为该断裂带是主要的发震构造。仙游序列ML5.0级最大地震前的震群活动序列参数计算结果显示,序列活动存在较为明显的前兆震群性质和衰减异常。     

福建德化小震群初步分析

2009年2月19日至2月26日,福建数字地震台网记录到在福建德化县境内发生了170次小地震序列活动,其中,最大震级为ML2．7。从震区地质背景、震源机制、地震活动和地震波形特征等方面进行了初步分析,并与2006年发生的最大震级ML2．0级德化震群进行了对比,计算了震群的序列特征参数,结果表明,震源机制解与北东向断裂带吻合,可能是该断层的应力调整,并且该震群具有前兆震群的某些特征。     

福建仙游地震序列的震源机制解

2010年8月4日至2013年10月4日福建仙游共记录到地震1209次,其中最大地震为2013年9月4日发生的ML5.0地震。为了加强对仙游地震序列的研究,更好地了解仙游地震的发震构造及震区的区域应力场,本文利用福建数字地震台网宽频带地震记录,采用矩张量反演方法,得到仙游地震序列中ML3.5的6次地震的震源机制解。这6次地震的震源机制解结果较为一致,都为走滑型地震,断层走向为NW向,倾角陡立,主压应力轴方向为近SN向。反演得到的主压应力轴方向与福建地区的区域应力场并不一致,本文认为仙游地震是由位于震区的金钟水库蓄水造成震区应力调整而引起的。     

NLLoc定位方法在福建地区的适用性探究

利用非线性定位方法NLLoc,对22次人工定点爆破事件和88次福建仙游震群序列M≥1.5级地震事件进行重新定位,并与福建台网日常定位方法进行对比,讨论了NLLoc方法在台网日常业务应用中的可行性.研究结果表明,NLLoc算法无论是人工爆破还是天然地震,其定位结果在发震时刻误差、震中误差和震源深度误差等方面都优于现有定位方法结果,尤其是在震源深度确定方面NLLoc算法优势明显.该方法定位仙游序列活动初期深度较浅与CAP反演2012年4月15日ML4.1级地震的震源深度一致,地震序列活动中后期深度均值略小于理论估值;而正式目录的地震序列活动初期深度较深,震源深度差值较大,地震序列活动中期深度均值大于理论估值.NLLoc方法可用于台网日常地震定位,且有助于更好地解决震源深度测定问题,提高地震定位精度.     

仙游地震序列中小地震震源机制解特征

利用福建地震台网记录的数字地震波形,采用基于P波初动和S/P振幅比(HASH)方法,反演了2010年8月至2014年12月间发生在福建仙游地区ML2.0级以上地震的震源机制解。结果表明,仙游地震序列中小地震震源机制解一致性较好,其节面走向、倾角及滑动角以及P、T轴优势分布十分明显。节面走向优势方向为北西向,与该区域沙县—南日岛断裂走向一致,震源破裂类型为近直立右旋走滑型。序列的发生主要受控于近南北向主压应力,与福建地区背景应力场方向存在一定差异。分析认为,仙游地震序列的发生主要受控于仙游地区小尺度区域的构造应力场,金钟水库水位变化与序列显著地震活动存在一定相关性,但对仙游地区构造应力场影响不明显。     

福建仙游ML5.0级地震波形分析

2013年9月4日,福建仙游发生ML5.0级地震,这是福建数字地震台网建成以来记录到的该区域最大地震.本文就此次地震的记录波形进行分析,结果表明：仙游ML5.0级地震的震相出现规律符合一般近震记录特征;在波形中分析出sPn震相,并据此测定地震的震源深度为11.1 km,与Hyposat方法测定结果一致;用初至首波估算出震区的地壳厚度约为25.2 km.     

2022年四川马尔康MS6.0强震群重定位及发震断层探讨

2022年四川马尔康强震群是中国有地震台网记录以来，巴颜喀拉块体东部马尔康地区首次出现的地震频度高、时空分布集中、爆发性较强且震级强度大的罕见强震群活动。文中通过双差定位方法对该震群序列进行了重定位，利用gCAP方法测定了M_S≥3.6地震的震源机制及矩心深度，然后根据震源机制结果分析了马尔康地区应力体系与这些地震震源机制的关系，最后根据重定位结果进行了断层面拟合。结果显示，马尔康震群序列震中区域主要沿NW向优势分布，整个震群序列的平均初始破裂深度为9.8km,深度剖面反映地震相对密集的区域主要介于0～15km深度之间，震群中震级最大的M_S6.0地震的初始破裂深度为12.5km,几乎位于震群序列密集区的底端。其震源机制节面I的走向为150°,倾角为79°,滑动角为7°;节面Ⅱ的走向为59°,倾角为83°,滑动角为169°;矩心深度为9km。其余M_S≥3.6地震的震源机制均为走滑型，震源机制节面的倾角为71°～86°,且相同走向的各个节面的倾向也有所不同，其矩心深度为5～9km,P轴方位为NWW向，且倾伏角近水平。M     

福建水口及仙游地震序列的谱振幅相关系数变化特征

利用福建省数字地震台网记录的波形数据,计算了水口和仙游地震序列的谱振幅相关系数,结果显示水口序列谱振幅相关系数在0.90-0.98之间变化,相关系数高,序列地震震源机制解相似程度高;仙游序列谱振幅相关系数在0.72-0.81之间变化,相关系数略低,震源机制解整体相似程度不高。结合福建地区同期地震活动背景水平分析认为,较高的谱振幅相关系数与福建地区较高的背景应力积累水平存在一定相关性。水口和仙游序列谱振幅相关系数时序变化显示,序列最大地震发生前的谱振幅相关系数存在上升变化,显示较大地震发生前震区应力水平有增强迹象。     

用双子地震相干函数法对常熟震群进行精确相对定位

采用双子地震相干函数分析法利用江苏区域遥测地震台网数字化资料对2001年11月3-14日发生在江苏省常熟-张家港间的震群进行精确相对定位。主参考地震用区域地壳结构重新定位。结果表明:(1)主参考地震与区域遥测地震台网的定位相比偏离了10.61 km;(2)震群中地震的平面位置更集中;(3)各次地震的震源深度体现了震群特征。本文还对震群与构造的关系进行了分析,推测可能与顾山-虞山断裂有关。     

琼中地震台重力仪记录同震响应特征分析

2013年2月6-8日圣克鲁斯群岛发生6次强震,琼中地震台的重力仪记录都有同震响应出现。本文从重力仪记录的面波的延迟时间、最大变形幅度、同震持续时间3个方面研究了6次强震的同震响应特征。     

Contribution to the knowledge of the magmatic evolution by the study of the variation of the coefficient of viscosity

The determination of the coefficient of viscosity of eruptive products gives useful elements to the knowledge of possible variations of composition and physical conditions of the magmas.     

On the Mechanism of the Secular Tidal Acceleration of the Solid Inner Core and the Viscosity of the Liquid Core

As is known, the secular deceleration of the Earth's diurnal rotation is explained mainly by the tidal friction in the ocean. Below we consider this mechanism in some detail, taking into account also elastic deformations of the mantle under the action of ocean loading and the interaction between the tide-generating body, ocean tidal wave, liquid outer core, and solid inner core. It is shown that elastic displacements of the core-mantle boundary under the action of ocean loading are of about the same amplitude and phase as the elastic loading displacements of the Earth's outer surface. As a result, side by side with the mechanism of secular deceleration of diurnal rotation of the mantle, there are also (1) the opposite mechanism of secular acceleration of diurnal rotation of the outer liquid core and of the solid inner core and (2) the mechanism of excitation of differential rotation in the liquid core. Taking these effects into account, we compare theoretical and modern observed data on the eastward drift of the solid inner core. It is shown that the best agreement may be obtained if the turbulent viscosity of the liquid core is about 2 × 10 ³ Poise     

Comparison Between the Nutations of the Planet Mars and the Nutations of the Earth

The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth.     

Pictorial Series of the Manifestations of the Dynamics of the Earth

Studia Geophysica et Geodaetica -     

动水压力对深水桥墩地震响应影响的研究综述

地震激励下处于深水中的桥墩和周围水体的相互作用将对桥梁结构的动力响应产生较大影响。首先对地震作用下水-桥墩的相互作用理论做了概括,给出了动水压力对桥墩的作用效应及各自的适用范围;对主要的三种考虑流固耦合效应的分析方法做了对比,探讨了地震作用下影响水-结构相互作用的主要因素,并对今后的研究提出了建议。     

Evolution of the Source of the Active Region of the Sun

Geomagnetism and Aeronomy - The magnetic evolution of the active region of the Sun at the level of the photosphere has been studied. Magnetic synoptic maps of the 2007 Kitt Peak Observatory were...     

Magnetic stratigraphy of the Ordovician in the lower reach of the Kotuy River: the age of the Bysy-Yuryakh stratum and the rate of geomagnetic reversals on the eve of the superchron

Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary.     

On the solution of the reverse problem of geodesics with the help of the chord

Резюме Дается вывод формул для вычислений длины хорды, длины и азимутов нормаляных сечений и длины геодезической линии эллипсоида. Применяются тригонометрические функции данных величин и постоянные принятого ргфгргнц-эллипсоида, что является целесообразным при использовании вычислителQjных машин, особенно автоматов. Рабочие формулы рекомендуются в форме (8–11).

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Dedicated to Professor František Fiala on His 85th Birthday

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Address: Veveři 95, Brno.