Focal mechanism determination based on the polarity and SV-P amplitude ratio in the Kalabsha area, Aswan, Egypt

Mohamed, Haggag H.; Kang, Tae Cheon; Baag, Chang‐Eob

doi:10.1007/bf02910422

Cited by 7 publications

(4 citation statements)

References 7 publications

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“…We carefully pick polarities of impulsive P wave arrivals on vertical component seismograms. A grid search scheme (FocMec; Snoke et al, 1984) is used to test the full range of nodal plane orientations of double couple mechanisms with 10°increments. Takeoff angles were computed in the IGN velocity model (Rueda, 1995).…”

Section: Focal Mechanism Inversionmentioning

confidence: 99%

Focal Mechanisms for Subcrustal Earthquakes Beneath the Gibraltar Arc

Santos-Bueno

Fernandez-Garcia

Stich

et al. 2019

Geophysical Research Letters

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Intermediate deep earthquakes are usually associated with active subduction, and show mostly dip‐slip faulting mechanisms aligned with the downgoing oceanic lithosphere. Forty‐two new focal mechanisms from 50‐ to 100‐km depth beneath the Gibraltar Arc and Alboran Sea show different characteristics. The most abundant solutions are strike‐slip mechanisms, in agreement with relative plate motion between Nubia and Eurasia. Additional reverse faulting mechanisms indicate compression in direction of absolute plate motion, reproducing the basal drag of the mantle on the hanging lithosphere. In turn, no signature of ongoing subduction was found. Migrated sections of P wave receiver functions suggest that a significant part of intermediate deep seismicity is produced within the stalled remnants of Jurassic age, oceanic lithosphere that once formed the connection between the Alpine Tethys and the central Atlantic and later has been buried beneath the Gibraltar Arc.

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Section: Focal Mechanism Inversionmentioning

confidence: 99%

Focal Mechanisms for Subcrustal Earthquakes Beneath the Gibraltar Arc

Santos-Bueno

Fernandez-Garcia

Stich

et al. 2019

Geophysical Research Letters

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“…We determined the individual focal mechanisms for two events by using both P-wave first motion polarities and S/P amplitude ratio (SNOKE, 2003) as done by many authors (i.e., MOHAMED et al, 2001;KANG and BAAG, 2004;KANG and SHIN, 2006;PLENEFISCH and KLINGE, 2003;BADAWY et al, 2009;RITTER et al, 2009). Unfortunately, it was not possible to obtain well-constrained fault plane solutions for all the events because in many cases the azimuthal distribution of the DEU-GFZ stations was inadequate.…”

Section: Focal Mechanisms and Stress Tensor Inversionmentioning

confidence: 99%

An Assessment of the Seismicity of the Bursa Region from a Temporary Seismic Network

Gök

Polat

2011

Pure Appl. Geophys.

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A temporary earthquake station network of 11 seismological recorders was operated in the Bursa region, south of the Marmara Sea in the northwest of Turkey, which is located at the southern strand of the North Anatolian Fault Zone (NAFZ). We located 384 earthquakes out of a total of 582 recorded events that span the study area between 28.50-30.00°E longitudes and 39.75-40.75°N latitudes. The depth of most events was found to be less than 29 km, and the magnitude interval ranges were between 0.3 B M L B 5.4, with RMS less than or equal to 0.2. Seismic activities were concentrated southeast of Uludag Mountain (UM), in the Kestel-Igdir area and along the Gemlik Fault (GF). In the study, we computed 10 focal mechanisms from temporary and permanents networks. The predominant feature of the computed focal mechanisms is the relatively widespread near horizontal northwest-southeast (NW-SE) T-axis orientation. These fault planes have been used to obtain the orientation and shape factor (R, magnitude stress ratio) of the principal stress tensors (r 1 , r 2 , r 3 ). The resulting stress tensors reveal r 1 closer to the vertical (oriented NE-SW) and r 2 , r 3 horizontal with R = 0.5. These results confirm that Bursa and its vicinity could be defined by an extensional regime showing a primarily normal to oblique-slip motion character. It differs from what might be expected from the stress tensor inversion for the NAFZ. Different fault patterns related to structural heterogeneity from the north to the south in the study area caused a change in the stress regime from strike-slip to normal faulting.

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“…Because of the presence of the first local seismic network around the area, some detailed studies were carried out concerning the seismic activity in the area, for the safety purpose of the High Dam, e.g. Mohamed (1997;2001). Mohamed et al (2008) have modified the seismicity map of Aswan area during the period 1981-2006, which shows the following eight seismic clusters (Fig.…”

Section: Surface Geology Structural Setting and Seismicity Of The Res...mentioning

confidence: 99%

Subsurface structural mapping of Northern Nasser Lake region, Aswan, Egypt, using Bouguer data

Saleh

2011

Contributions to Geophysics and Geodesy

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In this study, we attempt to delineate the subsurface structures for the tectonic active region of Northern Nasser Lake using integrated interpretation techniques of gravity data with seismicity. The depths to the gravity sources, and the locations of the contacts of density contrast were estimated. Two methods were used for estimating source depths and contact locations: horizontal gradient (HG) and Euler deconvolution methods. Moreover, power spectral analysis, bandpass and upward continuation techniques were applied to evaluate the shallow and deep seated structures. Shallow depth structures were ranging between 0.30 km and 0.80 km. However, two average levels (interfaces) at depth 3.1 km and 7.2 km below the measuring level were revealed for the intermediate and deep seated structures respectively. Results of Euler deconvolution method suggested that, in the eastern part of the area, the basement could be observed on the ground and has become deeper in the central part. The interpreted structural map reveals that the area is affected by a set of faults trending mainly in the NW, E-W, N-S and NE-SW directions. Actually, this map has confirmed the idea that the intersections between the N-S and E-W striking faults along Nasser Lake area have generated seismic pulses. Moreover, three seismic zones (Z1, Z2 and Z3) are well correlated with the fault trends of the subsurface structures as derived from the horizontal gradient map. The present results suggest that there exist seismically-active fault east of High Dam, passing throughout Aswan reservoir from north to south. This fault is occupying region of high stress values which may generate large earthquakes in future, as it has long extension over several kilometers. Furthermore, the evaluated intruded volcanic bodies are found almost at the intersections between the E-W and NW oriented faults. Finally, the area is dissected by basement uplifts and troughs controlled mainly by the NW-SE faults.

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Focal mechanism determination based on the polarity and SV-P amplitude ratio in the Kalabsha area, Aswan, Egypt

Cited by 7 publications

References 7 publications

Focal Mechanisms for Subcrustal Earthquakes Beneath the Gibraltar Arc

Focal Mechanisms for Subcrustal Earthquakes Beneath the Gibraltar Arc

An Assessment of the Seismicity of the Bursa Region from a Temporary Seismic Network

Subsurface structural mapping of Northern Nasser Lake region, Aswan, Egypt, using Bouguer data

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