The July 9 and 23, 1905, Mongolian earthquakes: A surface wave investigation     

Emile A. Okal 《Earth and Planetary Science Letters》1977,34(2):326-331

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The July 9 and 23, 1905, Mongolian earthquakes: Further comments     

Emile A. Okal 《Earth and Planetary Science Letters》1978,41(1):110

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The 2004 Sumatra earthquake and Indian Ocean tsunami: What happened and why?     

Seth Stein  Emile A. Okal 《Visual Geosciences》2005,10(1):21-26

The December 26, 2004 Sumatra earthquake and the tsunami that followed killed over 300,000 people. In this paper, we analyze and discuss the geologic causes for this earthquake, the mechanisms that generated it, and follow up with a discussion on ways to prevent this type of disaster in the future.  相似文献   

Hydroacoustic signals generated by parked and drifting icebergs in the Southern Indian and Pacific Oceans     

Jacques Talandier  Olivier Hyvernaud  Dominique Reymond  Emile A. Okal 《Geophysical Journal International》2006,165(3):817-834

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Landslide Tsunamis: Recent Findings and Research Directions     

J.-P. Bardet  C. E. Synolakis  H. L. Davies  F. Imamura  E. A. Okal 《Pure and Applied Geophysics》2003,160(10-11):1793-1809

— Underwater landslides can trigger local tsunamis with high runup, endangering human life and devastating coastal cities, offshore structures, communication cables, and port facilities. Unfortunately, hazards from underwater landslides are not well understood and the extents of their potential damage remain difficult to ascertain at present. There is immediate need for multidisciplinary research to improve our understanding and plan countermeasures for mitigating their hazards. Conceived in the wake of the Papua New Guinea earthquake landslide and tsunami of 1998, this volume summarizes the state-of-the-art knowledge on underwater landslides and their potential to generate tsunamis from the multidisciplinary perspectives of observational and engineering seismology, geotechnical engineering, marine geology, and hydrodynamics. These various fields of engineering and science offer new synergetic opportunities to examine landslide tsunamis. This paper makes recommendations on future research directions, and will hopefully advance scientists' and engineers' understanding of these natural hazards and assist planners in mitigating their risks.  相似文献   

T Waves from the 1998 Papua New Guinea Earthquake and its Aftershocks: Timing the Tsunamigenic Slump   总被引：1，自引：0，他引：1  

Emile A. Okal 《Pure and Applied Geophysics》2003,160(10-11):1843-1863

— T waves recorded at hydrophone and seismic stations following the Papua New Guinea earthquake of 17 July 1998 and its aftershocks show that a small event at 09:02 GMT featured source properties incompatible with an elastic dislocation of appropriate body-wave magnitude (m _b=4.4). These include an exceptional duration (47 s at the Wake Island hydrophone station WK31), a spectrum rich in high frequencies (7 to 12 Hz), and a generally low spectral amplitude. These characteristics can be explained by the model of an underwater slump, accelerating from a standstill and eventually slowing down. The relocation of the 09:02 event is compatible with its location within an amphitheater inside which shipboard cruises in 1998 and 1999 documented the presence of a 4 – km³ geologically fresh slump. We propose that the slump took place at 09:02 on 17 July 1998, i.e., 13 minutes after the mainshock, and that it generated the locally catastrophic tsunami, whose properties (amplitude and distribution of runup; timing) could not be explained by a dislocation model.  相似文献   

Africa’s middle class: building houses and constructing identities in the small town of Buea,Cameroon     

Ben Page  Emile Sunjo 《Urban geography》2018,39(1):75-103

Across Africa households are commissioning new domestic buildings for their own use or to rent out rather than waiting for governments to supply urban shelter. We conceptualize this as two interwoven processes: building houses for a new middle class and the building of a new middle class identity. We draw particular attention to the impact of international migration on these processes. The paper uses quantitative data from building permits and qualitative data from 29 interviews and walk-round tours with homeowners and government officials in Buea, Cameroon. Despite some significant caveats (related to housing the urban poor, regulating building standards, and lost local government revenue), we argue that these individually initiated building projects do a reasonable job of meeting local demand for shelter. However, from the perspective of identity-building these buildings are less successful. Whilst homeowners take considerable pride in their building projects, the statements that these structures make about their identities are not always “read” by their neighbours in the way owners hope. New housing is the lens through which Buea’s residents interpret growing levels of inequality and its associated social tensions.  相似文献   

Quantification of Hydrophone Records of the 2004 Sumatra Tsunami     

Emile A. Okal  Jacques Talandier  Dominique Reymond 《Pure and Applied Geophysics》2007,164(2-3):309-323

The 2004 Sumatra-Andaman tsunami was recorded by hydrophones of the International Monitoring System at Site H08 near Diego Garcia, notably in frequency bands extending outside the range of the Shallow Water Approximation. Despite the severe high-pass filtering involved in this instrumentation, we show that the spectral amplitudes recovered around T = 87 s can be successfully explained by generation from the seismic source, in the framework of the normal mode theory of tsunami excitation. At the lower frequencies characteristic of more conventional tsunami waves (800 to 3200 s), the signal is probably present in the hydrophone records, but reliable deconvolution of its spectral amplitude is precluded by the fact that the instrumental filters lowered the tsunami signal to the level of resolution of the instrument digitizer. In the context of distant tsunami warning, hydrophone records could provide useful insight into high-frequency tsunami components, and even at lower, more conventional, frequencies, provided that an unfiltered channel could be recorded routinely.  相似文献   

Tsunami and its Hazard in the Indian and Pacific Oceans: Introduction   总被引：1，自引：0，他引：1  

K. Satake  E. A. Okal  J. C. Borrero 《Pure and Applied Geophysics》2007,164(2-3):249-259

The 2004 Indian Ocean tsunami caused an estimated 230,000 casualties, the worst tsunami disaster in history. A similar-sized tsunami in the Pacific Ocean, generated by the 1960 Chilean earthquake, commenced international collaborations on tsunami warning systems, and in the tsunami research community through the Tsunami Commission of International Union of Geodesy and Geophysics. The IUGG Tsunami Commission, established in 1960, has been holding the biannual International Tsunami Symposium (ITS). This volume contains selected papers mostly presented at the 22nd ITS, held in the summer of 2005. This introduction briefly summarizes the progress of tsunami and earthquake research as well as international cooperation on tsunami warning systems and the impact of the 2004 tsunami. Brief summaries of each paper are also presented.  相似文献   

Observed very long period Rayleigh-wave phase velocities across the Canadian shield     

Emile A. Okal 《Geophysical Journal International》1978,53(3):663-668

summary . The recent Indonesian earthquake (1977 August 19; M_s =8.0) makes possible a direct determination of Rayleigh-wave phase velocities at very long periods (200 to 300 s) over a pure shield path (College, Alaska-State College, Pennsylvania) by the two-station method. Results are in good agreement with previous models derived by regionalization of great-circle phase velocities and discussed in a previous paper (Okal, Paper I). Great-circle phase velocities computed at College and State College are correctly predicted by the models derived in Paper I, and further substantiate one of its main conclusions: no substantial structural differences between oceans and continents at depths greater than 240 km, are necessary to account for the presently available seismic data.  相似文献