K-means cluster analysis and seismicity partitioning for Pakistan   总被引：2，自引：2，他引：0  

Khaista Rehman  Paul W. Burton  Graeme A. Weatherill 《Journal of Seismology》2014,18(3):401-419

Pakistan and the western Himalaya is a region of high seismic activity located at the triple junction between the Arabian, Eurasian and Indian plates. Four devastating earthquakes have resulted in significant numbers of fatalities in Pakistan and the surrounding region in the past century (Quetta, 1935; Makran, 1945; Pattan, 1974 and the recent 2005 Kashmir earthquake). It is therefore necessary to develop an understanding of the spatial distribution of seismicity and the potential seismogenic sources across the region. This forms an important basis for the calculation of seismic hazard; a crucial input in seismic design codes needed to begin to effectively mitigate the high earthquake risk in Pakistan. The development of seismogenic source zones for seismic hazard analysis is driven by both geological and seismotectonic inputs. Despite the many developments in seismic hazard in recent decades, the manner in which seismotectonic information feeds the definition of the seismic source can, in many parts of the world including Pakistan and the surrounding regions, remain a subjective process driven primarily by expert judgment. Whilst much research is ongoing to map and characterise active faults in Pakistan, knowledge of the seismogenic properties of the active faults is still incomplete in much of the region. Consequently, seismicity, both historical and instrumental, remains a primary guide to the seismogenic sources of Pakistan. This study utilises a cluster analysis approach for the purposes of identifying spatial differences in seismicity, which can be utilised to form a basis for delineating seismogenic source regions. An effort is made to examine seismicity partitioning for Pakistan with respect to earthquake database, seismic cluster analysis and seismic partitions in a seismic hazard context. A magnitude homogenous earthquake catalogue has been compiled using various available earthquake data. The earthquake catalogue covers a time span from 1930 to 2007 and an area from 23.00° to 39.00°N and 59.00° to 80.00°E. A threshold magnitude of 5.2 is considered for K-means cluster analysis. The current study uses the traditional metrics of cluster quality, in addition to a seismic hazard contextual metric to attempt to constrain the preferred number of clusters found in the data. The spatial distribution of earthquakes from the catalogue was used to define the seismic clusters for Pakistan, which can be used further in the process of defining seismogenic sources and corresponding earthquake recurrence models for estimates of seismic hazard and risk in Pakistan. Consideration of the different approaches to cluster validation in a seismic hazard context suggests that Pakistan may be divided into K?=?19 seismic clusters, including some portions of the neighbouring countries of Afghanistan, Tajikistan and India.  相似文献   

Earthquake-induced landslide displacement attenuation models and application in probabilistic seismic landslide displacement analysis     

Graeme H.McVerry 《地震工程与工程振动(英文版)》2010,9(2):177-187

A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model,a New Zealand earthquake record data set with magnitudes ranging from 5.0 to 7.2 within a source distance of 175 km is used. The model can be used to carry out deterministic landslide displacement analysis,and readily extended to carry out probabilistic seismic landslide displacement analysis. DLL attenuation models have also been developed by using earthquake source terms,such as magnitude and source distance,that account for the effects of earthquake faulttype,source type,and site conditions. Sensitivity analyses show that the predicted DLL values from the new models are close to those from the Romeo model that was developed from an Italian earthquake record data set. The proposed models are also applied to an analysis of landslide displacements in the Wenchuan earthquake,and a comparison between the predicted and the observed results shows that the proposed models are reliable,and can be confidently used in mapping landslide potential.  相似文献   

Temporary Migration and the Labour Market in Australia     

Graeme Hugo 《The Australian geographer》2006,37(2):211-231

Australia's labour market is most influenced by international migration among OECD nations, but Australian research on this issue focuses almost exclusively on permanent settlement migration. The present paper, however, demonstrates that non-permanent migration has an important impact on the Australian labour market, although such migrants are not included in standard data collections and research on migrants and the labour market. A number of data sources are utilised to estimate the labour-market impact of Working Holiday Makers, Temporary Business Entrants, Overseas Students, and New Zealand temporary migrants. It is shown that their impact is equivalent to more than 400?000 full-time jobs. However, the effect is magnified because it is concentrated in particular sectors of the economy and in particular communities within Australia. A number of issues relating to temporary migration are discussed, including the nature of its relationship with permanent migration, the effects on job training, and the implications for regional development.  相似文献   

A ~ 40-year paleoenvironmental record from the Swan Oxbow,Yangtze River,China, inferred from testate amoebae and sedimentary pigments     

Qin  Yangmin  Zhang  Lihua  Swindles  Graeme T.  Yang  Huan  Gu  Yansheng  Qi  Shihua 《Journal of Paleolimnology》2021,66(1):29-40

Journal of Paleolimnology - We present a?~?40–year record of environmental change in the Swan Oxbow, Yangtze River, China, inferred from testate amoeba and sedimentary pigment...  相似文献   

The Southern Oscillation,environmental anomalies,and mortality of two Southern African seabirds     

Graeme D. La Cock 《Climatic change》1986,8(2):173-184

Mass mortalities and breeding failures of seabirds in the Pacific Ocean have been directly or indirectly linked to local manifestations of the Southern Oscillation. Similar seabird mortalities have been reported in the Benguela upwelling system along the southern African coast. A Boolean factor analysis of binary data (occurrence vs. non-occurrence) showed that certain worldwide and southern African anomalous climatic events tended to co-occur in the same year, and that seabird mortalities and scarcities of small fish along the southern African coast occurred in either the same year, or the year before, the anomalous climatic events. The environmental conditions leading up to warm-water events in southern Africa appear as detrimental to seabird populations as the warm-water events themselves.  相似文献