scholarly journals Precursory change of aftershock activity before large aftershock. A case study for recent earthquakes in China.

1989 ◽  
Vol 37 (3) ◽  
pp. 155-177 ◽  
Author(s):  
Zhixin ZHAO ◽  
Kazuo MATSUMURA ◽  
Kazuo OIKE
1979 ◽  
Vol 16 (9) ◽  
pp. 1892-1898 ◽  
Author(s):  
R. B. Horner ◽  
R. J. Wetmiller ◽  
H. S. Hasegawa

The St-Donat earthquake of February 18, 1978, occurred in a diffuse zone of significant seismicity in western Quebec. A field survey detected two aftershocks ([Formula: see text]) in a 3 day period following the magnitude mb(Lg) 4.1 main shock. These were followed by a magnitude mb(Lg) 3.4 earthquake on February 23, after the field stations were removed. Main shock and aftershock activity occurred within a small active volume located at 46 °19.2′N, 74°06.6′W, depth 7 km, with an estimated uncertainty of 1 km on all three hypocentral parameters. The main shock seismic moment was calculated to be 0.8 × 1022 dyne∙cm (8 × 1022 μN∙cm).The tremor was felt over an area of 70 000 km2 in western Quebec, eastern Ontario, and northern New York State with a maximum radius of perceptibility of 185 km and a maximum intensity of V in the St-Donat area. A comparison of the isoseismals of this and three other recent earthquakes of magnitude near 4 suggests a variation of maximum intensity inversely with focal depth; a significant area of intensity V is only observed when the focal depth is less than 10 km. There is also an indication of a systematic change in focal depths across the western Quebec zone, from shallow (upper crustal) depths north of Montreal to deeper (midcrustal) depths north of Ottawa.The P-nodal solution indicates almost pure thrust motion on a plane striking N20°W and dipping either 40°NE or 50°SW. The deviatoric compression axis is nearly horizontal, in a west-southwest direction. Similar results from the 1975 Maniwaki, Quebec, earthquake suggest that a uniform stress condition exists throughout western Quebec.


Nature ◽  
1933 ◽  
Vol 132 (3336) ◽  
pp. 543-543

2011 ◽  
Vol 05 (05) ◽  
pp. 493-508 ◽  
Author(s):  
NING-SHENG CHEN ◽  
GUI-SHENG HU ◽  
MING-FENG DENG ◽  
WEI ZHOU ◽  
CHENG-LIN YANG ◽  
...  

This paper describes a study about the impact of earthquakes on debris flows with a focus on the Great Wenchuan Earthquake 2008 in China. The land form, precipitation, and source material are the three key factors for debris flow initiation in the Wenchuan surrounding area. Classifications and examples of four types of debris flow initiation triggering (gully triggering, slope triggering, liquefaction triggering, and gully erosion triggering) have been presented. The initiation mechanisms are attributed to hydraulic and geomechanical aspects. The actual debris flow cases linked with the Great Wenchuan Earthquake and other earthquakes in China have been used to illustrate the increased magnitudes of debris flows due to a large amount of loose materials created by the seismic actions. The critical precipitation for debris flows is reduced by the earthquake. It is predicted that the impact of the Great Wenchuan Earthquake on the local debris flows would be significant in the next 5–6 years, and much less in the following years (up to 20 years). Finally, the debris flow system will reach a relative stable stage. This prediction is based on the historical observations at other earthquake areas and the qualitative analysis on debris flow initiation mechanisms.


2014 ◽  
Vol 44 (2) ◽  
pp. 218-224 ◽  
Author(s):  
Yu Huang ◽  
Miao Yu ◽  
Subhamoy Bhattacharya

2015 ◽  
Vol 724 ◽  
pp. 358-361
Author(s):  
Da Wei Lu ◽  
Zhi Bo Yang

Strong earthquake motion observations have gathered much useful data for the seismic-resistant design of civil engineering structures, and for developing earthquake prevention technology. The performance of Chinese strong motion network has been evaluated from recent earthquakes in Chinese Mainland. To follow the new requirement of the earthquake mitigation plan, some new practice of strong motion observations are described, including rapid urban ShakeMap, earthquake early warning system.


2019 ◽  
Vol 2 (3) ◽  
pp. 160
Author(s):  
Mariateresa Guadagnuolo ◽  
Giorgio Frunzio ◽  
Michelina Monaco ◽  
Anna Tafuro

Recent earthquakes have shown the seismic vulnerability of the Italian Architectural heritage and the need of interventions. The restoration design should take into account not only assessment and rehabilitation, but also the need of fruition of the cultural assets. These aspects have been considered in the last Italian seismic codes, a performance-based set of technical requirements to be addressed in the design process. In this framework, the requirements that the materials, meant to repair or replace historic ones, should fulfill are a key issue. In particular, for tuff masonry structures, the evaluation of the mechanical characteristics of the mortar is essential. Tests performed directly on samples withdrawn on site are perhaps the most reliable tools to determine the strength characteristics of a mortar to be used for restoration. Unfortunately, the possible dimensions of the samples are not compatible with the minimum required for a reliable mechanical test, so that the characterization of the old mortars and their historic context can be made obtaining information by the treatises of the time: components and their proportions, together with curing operations are often reported in the manuals. In particular, in the Middle Age the Roman knowledge about pozzolanic mortars was somewhat lost, and the results can be seen in the durability problems of several monuments of the period. These last considerations are the motivations of this paper, in which a study of the pozzolanic mortars in tuff masonry structures is provided. As a case study, the tuff masonry structures of the Paleocristian Basilica in Cimitile are considered and examined.


Author(s):  
C. Palestini ◽  
A. Basso ◽  
L. Graziani

The contribution, considering the use of low-cost photogrammetric detection methodologies and the use of asset Historical-BIM, has as its aim the theme of knowledge and the adaptation of safety in school buildings, a topic brought to attention by the many situations of seismic risk that have interested the central Apennines in Italy. The specific investigation is referred to the Abruzzo region, hit by the recent earthquakes of 2016 and 2009 that have highlighted the vulnerability of the building structures involved in a large seismic crater covering large areas of the territory. The need to consider in advance the performance standards of building components, especially concerning the strategic ways of the functions contained in them, starts here. In this sense, the school buildings have emerged among the types on which to pay attention, a study theme to be promptly considered, considering the functions performed within them and the possible criticality of such constructions, often dated, enlarged or readjusted without appropriate seismic adaptation plans. From here derives the purpose of the research that is directed towards a systematic recognition of the scholastic heritage, deriving from objective and rapid surveys at low cost, taking into consideration the as-built and the different formal and structural aspects that define the architectural organisms to analyse and manage through three-dimensional models that can be interrogated using HBIM connected to databases containing information of a structural and functional nature. In summary, through the implementation of information in the BIM model, it will be possible to query and obtain in real time all the necessary information to optimize, in terms of efficiency, costs, and future maintenance operations.


2014 ◽  
Vol 38 (01) ◽  
pp. 102-129
Author(s):  
ALBERTO MARTÍN ÁLVAREZ ◽  
EUDALD CORTINA ORERO

AbstractUsing interviews with former militants and previously unpublished documents, this article traces the genesis and internal dynamics of the Ejército Revolucionario del Pueblo (People's Revolutionary Army, ERP) in El Salvador during the early years of its existence (1970–6). This period was marked by the inability of the ERP to maintain internal coherence or any consensus on revolutionary strategy, which led to a series of splits and internal fights over control of the organisation. The evidence marshalled in this case study sheds new light on the origins of the armed Salvadorean Left and thus contributes to a wider understanding of the processes of formation and internal dynamics of armed left-wing groups that emerged from the 1960s onwards in Latin America.


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