scholarly journals Instrumental and field observations for the determination of the seismogenic structure of the 7 September 1999 Athens earthquake

2001 ◽  
Vol 34 (4) ◽  
pp. 1457 ◽  
Author(s):  
Γ. Α. ΠΑΠΑΔΟΠΟΥΛΟΣ ◽  
Α. ΓΚΑΝΑΣ ◽  
Σ. ΠΑΥΛΙΔΗΣ
Keyword(s):  
Main Shock ◽  
Hanging Wall ◽  
Strong Motion ◽  
Small Scale ◽  
Foot Wall ◽  
Seismogenic Structure ◽  
Rock Falls ◽  
Field Evidence ◽  
Athens Earthquake ◽  
Fili Fault

The earthquake of 7 Sept. 1999 (Ms= 5.9) that struck the metropolitan area of Athens, occurred only at a distance of '18 NW from the historical center of the city and has been the most destructive shock in modern history of Greece. Therefore, it is of great importance to identify the seismogenic structure. Focal mechanisms of the main shock as well as the lateral and vertical distributions of the aftershocks , determined by several institutes, are consistent in that the main shock was associated with a normal faulting striking WNE-ESE and dipping SW. The only geological faults known in the area to have the geometrical characteristics that are compatible with the seismographic results are the fault of Thriassion Pedion and the Fili fault. We support that the Fili fault, striking 110° - 150° Ν at an observable length of 8-10 Km, has been very probably the seismogenic structure of the Athens earthquake because ( i) it proved to be an active fault as revealed by the striations we observed on several segments of the fault mirror, ( ii) the meizoseismal region as well as the most important ground failures, like local small-scale landslides and rock-falls, all are located on the hanging-wall domain and very close to the surface trace of the fault as it is theoretically expected (e.g. Oglesby et al., 2000), ( iii) we observed a possibly co-seismic displacement by 3-6 cm of the SW (hanging-wall) segment towards SW . On the contrary, the fault of Thriassion Pedion is recognizable in satellite images but in the field it is evident only as a series of alluvium cones which is an evidence of a possibly inactive structure. Moreover, the meizoseismal area and the ground failures observed in association with the Athens earthquake are located in its foot-wall, that is in the domain where strong motion should not expected to occur. In addition, if that fault was the seismogenic one then the earthquake focus would fit the fault geometry only if it was shifted at least 15 km southwestwards. The last possibility that the Athens earthquake was associated with a blind fault is not supported by any kind of instrumental or field evidence.

Validation of Coupled FDM-DEM Approach on the Soil-Raft Foundation Interaction Subjected to Normal Faulting

2021 ◽  
Author(s):  
Fang Ru-Ya ◽  
Lin Cheng-Han ◽  
Lin Ming-Lang
Keyword(s):  
Active Fault ◽  
Ground Deformation ◽  
Numerical Models ◽  
Hanging Wall ◽  
Normal Fault ◽  
Small Scale ◽  
Foot Wall ◽  
Normal Faulting ◽  
Raft Foundation ◽  
Overburden Soil

<p>Recent earthquake events have shown that besides the strong ground motions, the coseismic faulting often caused substantial ground deformation and destructions of near-fault structures. In Taiwan, many high-rise buildings with raft foundation are close to the active fault due to the dense population. The Shanchiao Fault, which is a famous active fault, is the potentially dangerous normal fault to the capital of Taiwan (Taipei). This study aims to use coupled FDM-DEM approach for parametrically analyzing the soil-raft foundation interaction subjected to normal faulting. The coupled FDM-DEM approach includes two numerical frameworks: the DEM-based model to capture the deformation behavior of overburden soil, and the FDM-based model to investigate the responses of raft foundation. The analytical approach was first verified by three  benchmark cases and theoretical solutions. After the verification, a series of small-scale sandbox model was used to validate the performance of the coupled FDM-DEM model in simulating deformation behaviors of overburden soil and structure elements. The full-scale numerical models were then built to understand the effects of relative location between the fault tip and foundation in the normal fault-soil-raft foundation behavior. Preliminary results show that the raft foundation located above the fault tip suffered to greater displacement, rotation, and inclination due to the intense deformation of the triangular shear zone in the overburden soil. The raft foundation also exhibited distortion during faulting. Based on the results, we suggest different adaptive strategies for the raft foundation located on foot wall and hanging wall if the buildings are necessary to be constructed within the active fault zone. It is the first time that the coupled FDM-DEM approach has been carefully validated and applied to study the normal fault-soil-raft foundation problems. The novel numerical framework is expected to contribute to design aids in future practical engineering.</p><p><strong>Keywords</strong>: Coupled FDM-DEM approach; normal faulting; ground deformation; soil-foundation interaction; raft foundation.</p>

scholarly journals Numerical Investigation of Factors Influencing Oil and Gas Lifelines Behavior due to Normal Faulting Geo-Hazard

2015 ◽  
Vol 10 (Special-Issue1) ◽  
pp. 806-813
Author(s):  
Reza Khaksar ◽  
Majid Moradi
Keyword(s):  
Oil And Gas ◽  
Hanging Wall ◽  
Small Scale ◽  
Foot Wall ◽  
Buried Pipeline ◽  
Normal Faulting ◽  
Geotechnical Centrifuge ◽  
Centrifuge Model ◽  
Factors Influencing ◽  
Centrifuge Model Tests

In this study, some factors influencing the response of buried oil and gas lifelines subjected to normal faulting are investigated. Due to such phenomenon, the stress, strain and displacement are induced in pipeline. Finite element code of Abaqus has been employed to model pipe and its surrounding soil considering material nonlinearities, soil-pipe interaction and foot wall and hanging wall interface. The numerical model has been calibrated through some small scale geotechnical centrifuge model tests and based on such calibrated model, some factors influencing the response of buried pipeline has been investigated.

scholarly journals Analysis and Monitoring of Small-Scale Rock Fracture Zone Deformation and Shaft Failure in a Metal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Rong Lu ◽  
Fengshan Ma ◽  
Jie Zhao ◽  
Jianbo Wang ◽  
Guilin Li ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Rock Fracture ◽  
Hanging Wall ◽  
Wall Rock ◽  
Ground Movement ◽  
Small Scale ◽  
Foot Wall ◽  
Fracture Zones ◽  
Metal Mine ◽  
Deep Fracture

Rock fracture zones were distributed in a metal mine, and their deformation was always neglected because they are available on a small scale. However, the deformation of the small-scale fracture zone may lead to serious consequences, such as underground building and structure failure. Combined with the ground movement and surface fissure monitoring, the deformation of several fracture zones was analyzed by field monitoring, experimental test, and numerical simulation. The results showed that fracture deformation promoted the surface fissure movement. The horizontal movement of the foot wall rock of the fracture was found to be larger than the hanging wall rock. Deep mining engineering resulted in the squeezing of the shallow fracture, and the shallow fracture deformed more severely than the deep fracture. In the study area, fracture zone displacements were estimated according to a numerical model. The deformation and stress comparison of the shallow fracture zone and the deep fracture zone provided the characteristic of the broken structure in the field investigation.

THE EMPIRICAL GREEN’S FUNCTION TECHNIQUE MODIFICATION FOR ACCELEROGRAM SYNTHESIS IN LOWSEISMICITY REGIONS

2018 ◽  
Vol 12 (5-6) ◽  
pp. 72-80
Author(s):  
A. A. Krylov
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Main Shock ◽  
Amplitude Spectrum ◽  
Strong Motion ◽  
Function Technique ◽  
Focal Region ◽  
Empirical Green’S Function ◽  
Epicentral Zone ◽  
Empirical Green's Function

In the absence of strong motion records at the future construction sites, different theoretical and semi-empirical approaches are used to estimate the initial seismic vibrations of the soil. If there are records of weak earthquakes on the site and the parameters of the fault that generates the calculated earthquake are known, then the empirical Green’s function can be used. Initially, the empirical Green’s function method in the formulation of Irikura was applied for main shock record modelling using its aftershocks under the following conditions: the magnitude of the weak event is only 1–2 units smaller than the magnitude of the main shock; the focus of the weak event is localized in the focal region of a strong event, hearth, and it should be the same for both events. However, short-termed local instrumental seismological investigation, especially on seafloor, results usually with weak microearthquakes recordings. The magnitude of the observed micro-earthquakes is much lower than of the modeling event (more than 2). To test whether the method of the empirical Green’s function can be applied under these conditions, the accelerograms of the main shock of the earthquake in L'Aquila (6.04.09) with a magnitude Mw = 6.3 were modelled. The microearthquake with ML = 3,3 (21.05.2011) and unknown origin mechanism located in mainshock’s epicentral zone was used as the empirical Green’s function. It was concluded that the empirical Green’s function is to be preprocessed. The complex Fourier spectrum smoothing by moving average was suggested. After the smoothing the inverses Fourier transform results with new Green’s function. Thus, not only the amplitude spectrum is smoothed out, but also the phase spectrum. After such preliminary processing, the spectra of the calculated accelerograms and recorded correspond to each other much better. The modelling demonstrate good results within frequency range 0,1–10 Hz, considered usually for engineering seismological studies.

Control of rupture by fault geometry during the 1966 parkfield earthquake

1981 ◽  
Vol 71 (1) ◽  
pp. 95-116 ◽  
Author(s):  
Allan G. Lindh ◽  
David M. Boore
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
San Andreas Fault ◽  
Strong Motion ◽  
P Wave ◽  
Fault Geometry ◽  
Dynamic Rupture ◽  
San Andreas ◽  
Hill Station ◽  
Parkfield Earthquake

abstract A reanalysis of the available data for the 1966 Parkfield, California, earthquake (ML=512) suggests that although the ground breakage and aftershocks extended about 40 km along the San Andreas Fault, the initial dynamic rupture was only 20 to 25 km in length. The foreshocks and the point of initiation of the main event locate at a small bend in the mapped trace of the fault. Detailed analysis of the P-wave first motions from these events at the Gold Hill station, 20 km southeast, indicates that the bend in the fault extends to depth and apparently represents a physical discontinuity on the fault plane. Other evidence suggests that this discontinuity plays an important part in the recurrence of similar magnitude 5 to 6 earthquakes at Parkfield. Analysis of the strong-motion records suggests that the rupture stopped at another discontinuity in the fault plane, an en-echelon offset near Gold Hill that lies at the boundary on the San Andreas Fault between the zone of aseismic slip and the locked zone on which the great 1857 earthquake occurred. Foreshocks to the 1857 earthquake occurred in this area (Sieh, 1978), and the epicenter of the main shock may have coincided with the offset zone. If it did, a detailed study of the geological and geophysical character of the region might be rewarding in terms of understanding how and why great earthquakes initiate where they do.

Epicentral intensities and damage in the Hebgen Lake, Montana, earthquake of August 17, 1959

1962 ◽  
Vol 52 (2) ◽  
pp. 181-234
Author(s):  
Karl V. Steinbrugge ◽  
William K. Cloud
Keyword(s):  
Ground Motions ◽  
Strong Motion ◽  
Fault Scarp ◽  
Rock Falls ◽  
Small Unit ◽  
The Earth ◽  
Major Fault ◽  
Seismograph Station ◽  
Fault Scarps ◽  
Earth Fill

ABSTRACT An extensive fault scarp system was formed during the Hebgen Lake earthquake of August 17, 1959 (11:37:15 p.m., M.S.T., Gutenberg-Richter magnitude 7.1). Bedrock beneath Hebgen Lake warped, rotated, and caused a seiche in the lake. A major landslide dammed Madison Canyon, causing a lake to form above the slide. An estimated 19 persons were buried by the slide. Other slides and rock falls took out sections of the main highway north of Hebgen Lake and closed many roads in Yellowstone Park. Small unit masonry structures as well as wooden buildings along the major fault scarps usually survived with little damage when subjected only to vibratory forces. The unit masonry buildings, in particular, had little or no earthquake bracing. Intensity at the major scarp has been given a Modified Mercalli Scale rating of X. However, the maximum intensity ratings based on vibratory motion even a few feet away from the scarps were VII or VIII. Within the limits of observation there was little or no reduction in vibratory intensity 5 to 10 miles away compared to that at the fault. This is not to say that the ground motions were similar. At the closest strong-motion seismograph station (Bozeman, 58 miles from the epicenter) maximum recorded acceleration was about 7 per cent gravity. The earthquake was generally felt in about a 600,000 square mile area, mostly north of the instrumental epicenter. The earth-fill Hebgen Dam was within 1000 feet of a major scarp. The dam was significantly damaged, but it continued to be an effective structure.

scholarly journals Seismotectonic setting of the earthquake of august 7, 2016 and its aftershocks

2019 ◽  
pp. 156-167 ◽  
Author(s):  
I. A. Sanina ◽  
G. N. Ivanchenko ◽  
E. M. Gorbunova ◽  
N. L. Konstantinovskaya ◽  
M. A. Nesterkina ◽  
...  
Keyword(s):  
Main Shock ◽  
Satellite Image ◽  
External Influence ◽  
Visual Interpretation ◽  
Seismogenic Structure ◽  
Vertical Movements ◽  
Southern Boundary ◽  
East European ◽  
Alpine Zone ◽  
Axial Part

An earthquake with magnitude 4.8 hit the vicinity of Mariupol close to the southern boundary of the East European Platform (EEP) on August 7, 2016. The main event was followed by the aftershocks with magnitudes ranging from 2.2 to 3.9 which lasted for five days. The region experiences external influence from the neotectonically active Alpine zone resulting in intraplate deformations, horizontal and vertical movements of the Earth’s surface, and seismicity. The sources of the main shock and aftershocks are located within the block bounded by the neotectonically active Maloyanisol, Kalmius, and Primorsky faults. A seismogenic structure traced by the submeridional Kalchik lineament zone is identified in the axial part of the block by the combined analysis of geological and geophysical data and visual interpretation of the satellite image. This neotectonically active zone hosts the epicenters of the main event and most of the aftershocks.

Seismology and Strong Ground Motions in the 2004 Niigata Ken Chuetsu, Japan, Earthquake

2006 ◽  
Vol 22 (1_suppl) ◽  
pp. 9-21 ◽  
Author(s):  
Jim Mori ◽  
Paul Somerville
Keyword(s):  
Main Shock ◽  
Ground Motions ◽  
Moment Tensor ◽  
Hanging Wall ◽  
Active Faults ◽  
Field Investigation ◽  
Extensive Field ◽  
Reverse Faulting ◽  
Significant Region ◽  
Strong Ground

The Niigata Ken Chuetsu earthquake was a shallow, moderate-sized event producing strong shaking and considerable land failure damage across a significant region of Niigata Prefecture in central Japan. Moment tensor solutions indicate the main shock as being pure reverse faulting on a fault striking 30° east of north, roughly parallel to the mapped active faults and to the structural trends of the region, with nodal planes that dip down to the west at about 50° and down to the east at about 40°. The main shock was followed by an unusual number of large aftershocks. An extensive field investigation identified only minor surface faulting. Hanging wall effects accompanied by unusually high accelerations were observed, with peak horizontal accelerations of 1.75 g recorded at Tohkamachi and 1.33 g recorded at Ojiya.

The 23 October 2011 MW7.0 Van (Eastern Turkey) Earthquake: Interpretations of Recorded Strong Ground Motions and Post-Earthquake Conditions of Nearby Structures

2014 ◽  
Vol 30 (2) ◽  
pp. 657-682 ◽  
Author(s):  
V. Akansel ◽  
G. Ameri ◽  
A. Askan ◽  
A. Caner ◽  
B. Erdil ◽  
...  
Keyword(s):  
Fault Plane ◽  
Ground Motions ◽  
Hanging Wall ◽  
Strong Motion ◽  
Thrust Fault ◽  
Building Structures ◽  
Epicentral Area ◽  
Historical Structures ◽  
Strict Compliance ◽  
Strong Ground

A major thrust-fault earthquake of MW = 7.0 occurred on 23 October 2011 at 10:41:21 UTC in the eastern Anatolian region of Turkey, severely affecting the nearby towns of Van and Erciş. In this study, a few strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. Also reported are the post-earthquake field observations for various types of structures, such as buildings, bridges, historical structures, tunnels, and dams within the vicinity of the fault plane. The spatial distribution of damage indicates a noticeable hanging-wall effect. The special-type structures are observed to experience far less damage, as opposed to the building structures in the region pointing to the need for strict compliance to seismic building code and the corresponding construction requirements.

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