The Kozani-Grevena (Greece) earthquake of 13 May 1995 revisited from a detailed seismological study

1997 ◽  
Vol 87 (2) ◽  
pp. 463-473
Author(s):  
D. Hatzfeld ◽  
V. Karakostas ◽  
M. Ziazia ◽  
G. Selvaggi ◽  
S. Leborgne ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Active Fault ◽  
Fault Plane ◽  
Ground Surface ◽  
Strong Motion ◽  
Normal Fault ◽  
Normal Faulting ◽  
Waveform Modeling ◽  
Epicentral Region ◽  
Better Than

Abstract The Kozani earthquake (Ms = 6.6) of 13 May 1995 is the strongest event of the decade in Greece and occurred in a region of low seismic activity. Using regional data and the strong-motion record at the Kozani station, we relocate the mainshock at 40.183° N and 21.660° E, beneath the Vourinos massif at a depth of 14.2 km. We also compute a focal mechanism by body-waveform modeling at teleseismic distance, which confirms a normal mechanism. The most likely plane strikes 240° ± 1° N and dips 40° ± 1° N with a centroid depth of 11 ± 1 km. Modeling of the strong-motion record at Kozani confirms that nucleation started at the eastern termination of the bottom of the fault. Six days after the mainshock, we installed a network of 40 portable seismological stations for one week around the epicentral region. Several thousand aftershocks were recorded, among which we locate 622 with a precision better than 1 km. We compute 181 focal mechanisms that mostly show normal faulting. The aftershock seismicity is restricted between 5 and 15 km depth and defines a plane dipping north at an angle of about 35°, consistent with the mainshock mechanism. Seismic activity with the same pattern of normal fault mechanisms is also seen on an antithetic fault connected to the main one at 12 km depth, which cuts the ground surface north of the Vourinos ophiolite massif in the Siatista valley. These results suggest two possibilities for the active fault plane; either it is the Deskati fault that is flat and dips with a constant angle, and therefore the surface breaks are secondary features, or, more likely, it is the Paleohori fault that is new, of listric shape, and located ahead of the Deskati fault, which was not active during the earthquake.

scholarly journals Seismic-Scale Evidence of Thrust-Perpendicular Normal Faulting in the Western Outer Carpathians, Poland

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1252
Author(s):  
Jan Barmuta ◽  
Krzysztof Starzec ◽  
Wojciech Schnabel
Keyword(s):  
Large Scale ◽  
Fault Plane ◽  
Normal Fault ◽  
Normal Faulting ◽  
Seismic Profiles ◽  
Horizontal Movement ◽  
Outer Carpathians ◽  
Differential Uplift ◽  
Seismic Scale ◽  
Detachment Surface

Based on the interpretation of 2D seismic profiles integrated with surface geological investigations, a mechanism responsible for the formation of a large scale normal fault zone has been proposed. The fault, here referred to as the Rycerka Fault, has a predominantly normal dip-slip component with the detachment surface located at the base of Carpathian units. The fault developed due to the formation of an anticlinal stack within the Dukla Unit overlain by the Magura Units. Stacking of a relatively narrow duplex led to the growth of a dome-like culmination in the lower unit, i.e., the Dukla Unit, and, as a consequence of differential uplift of the unit above and outside the duplex, the upper unit (the Magura Unit) was subjected to stretching. This process invoked normal faulting along the lateral culmination wall and was facilitated by the regional, syn-thrusting arc–parallel extension. Horizontal movement along the fault plane is a result of tear faulting accommodating a varied rate of advancement of Carpathian units. The time of the fault formation is not well constrained; however, based on superposition criterion, the syn -thrusting origin is anticipated.

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>

Edgecombe earthquake

1987 ◽  
Vol 20 (3) ◽  
pp. 201-249 ◽  
Author(s):  
M. J. Pender ◽  
T. W. Robertson
Keyword(s):  
Structural Damage ◽  
Ground Surface ◽  
Strong Motion ◽  
Normal Fault ◽  
Lateral Spreading ◽  
Ground Acceleration ◽  
Paper Mills ◽  
North West ◽  
The North ◽  
The Town

On March 2 1987, at 01h 42m 34s UT an earthquake of magnitude (ML) 6.3 occurred near 37.91°S, 176.79°E close to the town of Edgecumbe in the North Island, New Zealand. The depth is provisionally estimated to be 12 ± 1 km. Seismic activity in the general area during the previous week culminated in a foreshock on March 2 of ML 5.2 at 01h 35m 37s. Four aftershocks with magnitudes in excess of 5.0 occurred on March 2 at 01h 51m 08s (ML 5.6), 02h 07m 23s (ML 5.1), 06h 56m 32s (ML 5.2) and 07h 55m 09s (ML 5.2). The earthquakes occurred at the end of summer after a long period of dry weather. Modified Mercalli Intensities of MM IX have been reported in and around Edgecumbe, with possible instances of MM X. Strong motion accelerographs recorded peak ground acceleration of up to 0.33 g within 15 km of the epicentre. The main shock produced a complex series of surface scarps, the longest being about 7 km long striking SW from Edgecumbe. About 1.3 m maximum extension occurred across the scarp with the area to the north-west being downthrown by about a maximum of 1.5 m which continued to subside slowly. Other smaller normal fault traces have also been detected as well as compressional rolls. There was extensive evidence of level ground liquefaction and lateral spreading near rivers. Both these phenomena produced eruption of sands at the ground surface. Some wells were observed to have increased flows or increased pressures whilst others were had decreased flows. General regional subsidence of the alluvial plains in the area up to 2m has been confirmed by levelling completed within three weeks of the earthquake. Structural damage was confined to the alluvial plains in which the town of Edgecumbe is centred. The depth of sediments on the plains is not less than 350 m. There was extensive minor damage to roads. Severe damage to many houses and other single storey structures. A dairy factory complex in Edgecumbe, two paper mills in Kawerau and a paperboard mill in Whakatane all sustained damage, in some cases considerable. At present information on the damage in the paper mills is not available.

Reanalysis of the 1963 Baffin Island Earthquake (MS 6.2) and its Seismotectonic Environment

1990 ◽  
Vol 61 (3-4) ◽  
pp. 181-192 ◽  
Author(s):  
Henry S. Hasegawa ◽  
John Adams
Keyword(s):  
Fault Plane ◽  
Normal Fault ◽  
In Situ Stress ◽  
Baffin Island ◽  
Normal Faulting ◽  
Fault Plane Solutions ◽  
Transient Phenomena ◽  
Tension Axis ◽  
Plane Solution

Abstract The 1963 Baffin Island earthquake of MS 6.2 is reanalyzed to determine whether or not it involved normal faulting, as previously suggested. The revised fault-plane solution has nodal planes with strike 113°, dip 66°, rake 235° and strike 352°, dip 41°, rake 322°. The T-axis trends 227° and plunges 14°, and the P-axis trends 338° and plunges 55°. Thus though this solution confirms normal faulting, it suggests a larger strike-slip component than most previous studies. The tension axis is oriented SW, which is normal to the NW geographic trend of Baffin Island. We consider that the normal-fault regime could be a transient phenomena related to extensional stress in the glacial forebulge presently centered over northeast Baffin Island, and is associated with incomplete postglacial rebound. However, future geophysical measurements such as heat flow, in-situ stress and vertical uplift rate, as well as more fault-plane solutions are required to test this hypothesis.

scholarly journals Centrifuge modeling of normal faulting and underground tunnel in sandy soil deposit

2021 ◽  
Vol 44 (2) ◽  
pp. 1-13
Author(s):  
Ali Nabizadeh ◽  
Alireza Seghateh Mojtahedi
Keyword(s):  
Free Field ◽  
Soil Layer ◽  
Ground Surface ◽  
Normal Fault ◽  
Vertical Displacement ◽  
Centrifuge Modeling ◽  
Fault Rupture ◽  
Normal Faulting ◽  
Axis Parallel ◽  
Propagation Pattern

Earthquakes of large magnitudes cause fault ruptures propagation in soil layers and lead to interactions with subsurface and surface structures. The emergence of fault ruptures on or adjacent to the position of existing tunnels cause significant damage to the tunnels. The objective of this paper is to study the interaction of an embedded tunnel within a soil layer and the soil deformations imposed upon by normal faulting. A centrifuge modeling under 80-g acceleration was conducted to investigate the rupture propagation pattern for different relative tunnel positions. Compared with the free field condition, due to tunnel and normal fault rupture interactions, focused on soil relative density and tunnel rigidity in this research, found that they can dramatically modify the rupture path depending on the tunnel position relative to the fault tip. The tunnel diverts the rupture path to its sides. This study presents the normal fault-tunnel interaction with the tunnel axis parallel to the normal fault line, to examine the changes that take place in fault rupture plane locations, the vertical displacement of the ground surface with tunnel presence and the effect of tunnel rigidity and soil density on fault tunnel interaction.

scholarly journals THE CORINI ACTIVE FAULT IN SOUTHWESTERN VIOTIA REGION, CENTRAL GREECE: SEGMENTATION, STRESS ANALYSIS AND EXTENSIONAL STRAIN PATTERNS

2018 ◽  
Vol 40 (1) ◽  
pp. 297
Author(s):  
A. Ganas ◽  
V. Spina ◽  
N. Alexandropoulou ◽  
A. Oikonomou ◽  
G. Drakatos
Keyword(s):  
Stress Analysis ◽  
Active Fault ◽  
Finite Strain ◽  
Fault Plane ◽  
Active Faults ◽  
Normal Fault ◽  
Active Structure ◽  
Seismic Slip ◽  
Gulf Of Corinth ◽  
Extensional Strain

The Corini normal fault is an active structure of Quaternary age in Southwestern Viotia. This is a region of low finite strain, located between the Quaternary rifts of the Gulf of Corinth and the Gulf of Evia. The fault is segmented into several segments with an average strike of N58°E and dip direction to the SE. The architecture of the fault zone is characterized by a 15 cm thick gouge rock, observed along the fault plane on the footwall side. At several localities along strike we observed a well-defined basal strip of un-eroded fault plane that represents the width (uplift) of the last co-seismic slip. The width of the strip ranges 20-30 cm. Slip inversion data show a mean orientation ofsigmaS (leastprincipal stress) as Ν328Έ which implies similar kinematics with the active faults of the south coast of the Gulf of Corinth.

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

The 4 December 2015 Mw 7.1 Normal-Faulting Antarctic Plate Earthquake and Its Seismotectonic Implications

2020 ◽  
Vol 110 (3) ◽  
pp. 1090-1100
Author(s):  
Ronia Andrews ◽  
Kusala Rajendran ◽  
N. Purnachandra Rao
Keyword(s):  
Body Wave ◽  
Focal Depth ◽  
Normal Fault ◽  
Normal Faults ◽  
Oceanic Plate ◽  
Normal Faulting ◽  
Transform Faults ◽  
Wave Inversion ◽  
Spreading Ridges ◽  
Southeast Indian Ridge

ABSTRACT Oceanic plate seismicity is generally dominated by normal and strike-slip faulting associated with active spreading ridges and transform faults. Fossil structural fabrics inherited from spreading ridges also host earthquakes. The Indian Oceanic plate, considered quite active seismically, has hosted earthquakes both on its active and fossil fault systems. The 4 December 2015 Mw 7.1 normal-faulting earthquake, located ∼700  km south of the southeast Indian ridge in the southern Indian Ocean, is a rarity due to its location away from the ridge, lack of association with any mapped faults and its focal depth close to the 800°C isotherm. We present results of teleseismic body-wave inversion that suggest that the earthquake occurred on a north-northwest–south-southeast-striking normal fault at a depth of 34 km. The rupture propagated at 2.7  km/s with compact slip over an area of 48×48  km2 around the hypocenter. Our analysis of the background tectonics suggests that our chosen fault plane is in the same direction as the mapped normal faults on the eastern flanks of the Kerguelen plateau. We propose that these buried normal faults, possibly the relics of the ancient rifting might have been reactivated, leading to the 2015 midplate earthquake.

Elastic displacements in the near-field of a propagating fault

1969 ◽  
Vol 59 (2) ◽  
pp. 865-908
Author(s):  
N. A. Haskell
Keyword(s):  
Fault Plane ◽  
Near Field ◽  
Strong Motion ◽  
Dislocation Motion ◽  
Displacement Discontinuity ◽  
Wave Form ◽  
Strong Motion Station ◽  
Ramp Function ◽  
Wave Forms ◽  
Parkfield Earthquake

abstract Displacement, particle velocity, and acceleration wave forms in the near field of a propagating fault have been computed by numerical integration of the Green's function integrals for an infinite medium. The displacement discontinuity (dislocation) on the fault plane is assumed to have the form of a unilaterally propagating finite ramp function in time. The calculated wave forms in the vicinity of the fault plane are quite similar to those observed at the strong motion station nearest the fault plane at the Parkfield earthquake. The comparison suggests that the propagating ramp time function is roughly representative of the main features of the dislocation motion on the fault plane, but that the actual motion has somewhat more high frequency complexity. Calculated amplitudes indicate that the average final dislocation on the fault at the Parkfield earthquake was more than an order of magnitude greater than the offsets observed on the visible surface trace. Computer generated wave form plots are presented for a variety of locations with respect to the fault plane and for two different assumptions on the relation between fault length and ramp function duration.

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