Field Survey of the 27 February 2010 Chile Tsunami

On 27 February 2010, a magnitude M _w?=?8.8 earthquake occurred off the coast of Chile??s Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most coastal residents to spontaneously evacuate after the earthquake. Many of the tsunami victims were tourists in coastal campgrounds. The international tsunami survey team (ITST) was deployed within days of the event and surveyed 800?km of coastline from Quintero to Mehuín and the Pacific Islands of Santa María, Mocha, Juan Fernández Archipelago, and Rapa Nui (Easter). The collected survey data include more than 400 tsunami flow depth, runup and coastal uplift measurements. The tsunami peaked with a localized runup of 29?m on a coastal bluff at Constitución. The observed runup distributions exhibit significant variations on local and regional scales. Observations from the 2010 and 1960 Chile tsunamis are compared.     

Segment boundaries, the 1894 ruptures and strain patterns along the Atalanti Fault, Central Greece

The Atalanti Fault is a large active normal fault segment inside the Gulf of Evia Rift system (Central Greece), that last ruptured during the April 1894 earthquake sequence. Using structural and geomorphological interpretations of digitally processed Landsat TM satellite imagery, two regions of i) low topography, ii) minimum hinterland development and iii) transverse bedrock ridge development, 34 kilometres apart were identified; these regions are suggested to be segment boundaries constraining the length of the fault. From throw profiles and displaced syn-rift strata, we estimate a minimum slip of 810m at the central region of the fault (Tragana), increasing to a value of 1200 meters within the Asprorema embayment area. These figures averaged over a time span of 3 million years (age of oldest offset syn-rift), yield mean slip rates of at least 0.27 to 0.4 mm/year.Field studies were also conducted along the length of the Atalanti Fault Segment to reexamine and map the 1894 ruptures. The surface break is only preserved locally where the footwall comprises a resistant bedrock lithology (limestone), whilst the rest of the rupture noted in historical records propagated along the contact with the volcanic pre-rift, as well as within the syn-rift, and has since been eradicated due to man-made changes in surface morphology. The surface breaks appear not to have crossed over the segment boundaries that we propose, but seem to have ruptured the full length of the Atalanti Fault Segment, that is, 34km. These observations suggest that the 1894 rupture is the longest mapped within Central Greece. However, it remains unclear whether the ruptures were produced solely by the 27/4/1894 earthquake, or by two events, one week apart. We discuss the implications for fault-behavioural models and seismic hazards for the Atalanti area.     

Satellite-measured water vapor isotopologues across the Tianshan Mountains,central Asia

The satellite-based water vapor stable isotope measurements have been widely used in modern hydrological and atmospheric studies. Their use is important for arid areas where the precipitation events are limited, and below-cloud evaporation is strong. This study presents the spatial and temporal characteristics of water vapor isotopologue across the Tianshan Mountains in arid central Asia using the NASA Aura Tropospheric Emission Spectrometer (TES). The near-surface water vapor stable isotopes are enriched in summer and depleted in winter, consistent with the seasonality of precipitation isotopes. From the surface to 200 hPa, the isotope values in water vapor show a decreasing trend as the atmospheric pressure decreases and elevation rises. The vapor isotope values in the lower atmosphere in the southern basin of the Tianshan Mountains are usually higher than that in the northern basin, and the seasonal difference in vapor isotopes is slightly more significant in the southern basin. In addition, bottom vapor isotopologue in summer shows a depletion trend from west to east, consistent with the rainout effect of the westerly moisture path in central Asia. The isotopic signature provided by the TES is helpful to understand the moisture transport and below-cloud processes influencing stable water isotopes in meteoric water.     

The Fault that Caused the Athens September 1999 Ms = 5.9 Earthquake: Field Observations

On 7 September 1999 the Athens Metropolitan area (Greece) was hit by a moderate size (Ms = 5.9) earthquake. The severely damaged area is localized in the northwestern suburbs of the city, at the foothills of Mt. Parnitha (38.1°N, 23.6°E), about 18 km from the historic centre of Athens. In this paper, we present our results on the surface expression of the seismogenic structure. Methods applied were: field observations, geological mapping, fault geometry and kinematics, evaluation of macroseismic data, interpretation of LANDSAT images, construction of a DEM and application of shading techniques. Aftershock distribution and fault plane solutions were also considered. Our results suggest that the earthquake source is located within the NW-SE trending valley bearing a few outcrops of Neogene-Quaternary sediments across the south foothills of Mt. Parnitha, never known in the past to have been activated by such strong earthquakes. The earthquake occurred along a 10 km long normal fault, striking N110°–133° and dipping 64°–85°SW, extending from the Fili Fort (4th century BC) in the NNW to the Fili town and then to Ano Liossia, to the SSE. Tensional stress field with ₃ axis almost horizontal striking NNE-NE prevails in the area. The fault strike and the extensional direction (₃) are compatible with the focal mechanism of the main shock.     

Deformation patterns associated with the M5.9 Athens (Greece) earthquake of 7 September 1999

The static displacement field of the Athens 1999 earthquake has been numerically modeled by a BEM method and analysed from SAR interferometry images with compatible results: (a) for a fault that reaches the surface the subsidence field coincides with the hangingwall domain of the Fili neotectonic normal fault with maximum amplitude, d _max, 5.5–7 cm, which is consistent with the possibly co-seismic displacement of 6–10 cm observed in the field, the average fault dislocation of 5–8 cm found by the application of circular source models, and the displacement up to 6 cm predicted by empirical relations between magnitude and displacement; the field of uplift covers the footwall domain of the fault with d _max1.5 cm;d gradually decreases with distance from the fault at a gradient of 0.4 cm/km, (b) for a blind fault d _max is only 1.8 and 0.3 cm in the hangingwall and footwall, respectively, and the decay gradient becomes 0.15 cm/km, (c) the total deformation area is 15 km × 15 km and the Fili fault, with a preferred mean dip of 60°, constitutes the natural boundary between the subsidence and uplift areas. The macroseismic field pattern is similar with that of the static ground deformation. The majority of intensity values VI (MM and EMS-98 scales), are distributed within the hangingwall of the Fili fault, while the highest intensities (VIII and IX) concentrate very close to the Fili fault within its hangingwall domain. A gradual decrease of the intensities with the distance from the Fili fault is evident. Because of the similarity between the intensity distribution pattern and the static ground deformation pattern, we make the hypothesis that the latter predicts well enough the main characteristics of the former although the ground displacement is dominated by relatively low frequency as compared to the ground acceleration.     

List of Forthcoming Papers

Other Index

List of Forthcoming Papers     

希腊Ionian海Kefallinia转换断裂带的地震复发行为

采用历史地震资料和统计方法研究了希腊Ionian海Kefallinia转换断裂带的两条断层(Kdallinia和Lefkada)的整体强地震复发行为.研究发现,Kefallinia断层的地震复发行为表现出丛集性特征,存在时间可预测复发行为;Letkada断层的地震复发行为具有近随机性特征.不存在时间可预测及滑动可预测的复发行为.造成其地震复发行为不同的原因可能有:(a)沿Kefallinia断裂带走向,由静力触发引起的断层分段间的相互作用;(b)Lefkada断层的地震复发行为受北部和东部的断层系影响.另外,活跃期内地震复发间隔分布的分散性较大.可用韦伯(Weibull)分布近似描述;而平静期持续时间分布的分散性不够,这样的分布不便进行拟合.