Induced and Ambient Crustal Seismicity under the Ghawar Oil-Gas Fields, Saudi Arabia (original) (raw)

A moderate-sized earthquake of Mw 4.4 occurred in southwestern Saudi Arabia on 23 January 2014. The event is considered as the largest observed earthquake that has occurred in the epicentral area. To examine the seismogenic stress regime and resolve the fault plane ambiguity, the hypocenter locations and focal mechanisms were determined using well recorded waveforms of the broadband stations operated by the Saudi Geological Survey. The current analysis included dataset consisting of mainshock and a total number of 113 well-located after-shocks. Focal mechanism solutions of the mainshock and fifteen aftershocks were determined. The focal mechanism solutions were inverted using stress tensor inversion. It indicates that the maximum compressive stress, σ 1 , has a nearly shallow plunge (11.8°) of ESE orientation and minimum compressive stress, σ 3 , has a shallow plunge (0.3°) toward NNE. Our results obtained from precise earthquake locations, focal mechanism solutions and stress tensor inversion reveal dextral strike-slip faulting over the ENE-WSW striking plane. The analysis of Coulomb failure stress emphasized the causative fault of the 2014 Jizan earthquake sequence. The active fault implies a reactivation of a high-angle fault, buried in the Precambrian basement, which is conjugate to the Red Sea spreading axis and NNW-SSE Najd fault system. The present study provided an impetus toward understanding the seismogenic stress regime in a virgin area.

Badra-Amarah fault is located in the northeastern side of the Mesopotamian Zone at the Iraq-Iran border. This fault is the most seismically active fault in Iraq and it is located within the seismic zone that could suffer a major damage. The goal of this study is to investigate the seismic history and the focal mechanism solutions of Badra-Amarah fault. Additionally, recent stress regime of the fault area was derived by conducting formal stress inversion technique. The seismic history has been studied by using the source parameters of earthquakes from different catalogs, mainly from the IRSC catalog. The focal mechanism solutions were assembled from the GCMT project, which were analyzed in this study to derive the principal stress directions and their regimes. According to the seismic history of the study area, four seismic swarms occurred along the fault in August, 2008, June, 2009, August, 2009, and April, 2012 with magnitude of mainshocks ranges from 4.4 to 5.7. The focal mechanis...

Badra-Amarah fault is located in the northeastern side of the Mesopotamian Zone at the Iraq-Iran border. This fault is the most seismically active fault in Iraq and it is located within the seismic zone that could suffer a major damage. The goal of this study is to investigate the seismic history and the focal mechanism solutions of Badra-Amarah fault. Additionally, recent stress regime of the fault area was derived by conducting formal stress inversion technique. The seismic history has been studied by using the source parameters of earthquakes from different catalogs, mainly from the IRSC catalog. The focal mechanism solutions were assembled from the GCMT project, which were analyzed in this study to derive the principal stress directions and their regimes. According to the seismic history of the study area, four seismic swarms occurred along the fault in August, 2008, June, 2009, August, 2009, and April, 2012 with magnitude of mainshocks ranges from 4.4 to 5.7. The focal mechanis...

Abu Gharadig (AG) oil and gas field lies in the central portion of the AG basin in the northern part of the Western Desert. The Abu Roash " G " (AR " G ") represents the basal member of the Abu Roash Formation and comprises shale and limestone with interbeds of sandstone. This member may act as a source, reservoir or seal rock. Structural patterns of the AR " G " Member play an important role in the hydrocarbon potentialities and prospect identification in the area. The data available for the present study include four digital wireline logs, 2D seismic sections, well path data, formation tops and a checkshot survey. The goal of the present study was achieved through the interpretation of the 2D seismic sections using petrel schlumberger modeling software. Two-way time (TWT) and depth structure maps were obtained, in addition to the geo-seismic cross-sections. From the present study, it is concluded that the AR " G " Member suffered compartmentalization by a complex series of normal faults along with anticlinal folding. The anticline has NE-SW axis resulting from NW-SE compression. The fault planes have trends range from EW to NW-SE direction. The fold and the NW-SE faults are of Late Cretaceous age and are related to the time of the positive structural inversion through the AG basin. The fold is asymmetric and doubly plunging. The fold changes its asymmetry and plunging from SW to NE. The normal faults form horsts, grabens and half grabens.

The Gulf of Aqaba is considered one of the most seismotectonically active regions in the Middle East. This study analyzes the seismic activity from 1983 to 2018 to investigate the spatio-temporal distribution of the events in the Gulf’s three basins. The seismic activity is characterized by conventional mainshock–aftershock sequences and swarm activity. Most activity is located in the Aragonese basin, while the Dakar basin shows less seismic activity. The b-value was calculated for the three basins from the declustered catalogue, representing the fingerprint of the transform fault. Within the Aragonese, three significant earthquakes occurred in 1993, 1995, and 2015 with moment magnitude (Mw) of 5.8, 7.2, and 5.2, respectively. An intermediate seismic quiescence preceded the three earthquakes. The quiescence time for the 1995 earthquake began at the tail of the aftershocks of the 1993 mainshock, suggesting that the two earthquakes were not entirely independent. At the tail of the 199...

The Gulf of Aqaba is one of the most active places around Egypt, with several earthquake sequences having occurred there through ancient and modern times. In the last century, four earthquake sequences took place in the gulf (1983, 1990, 1993, and 1995). Recently, on 27 June 2015, a sequence of 96 earthquakes with local magnitudes ranging from 0.7 to 5.2 was recorded by the Egyptian National Seismological Network (ENSN). On 16 May 2016, another earthquake sequence started and continued for several consecutive days, with 95 events with local magnitudes ranging from 1.6 to 5.5 being centered south of the 27 June 2015 sequence. In this paper, we analyse the complete waveform and polarity data set of both earthquake sequences to determine their focal mechanisms and to update our knowledge of the stress field in the Gulf of Aqaba. Through the results obtained, we conclude that, the Gulf of Aqaba is affected by a primary structure of a left-lateral strike-slip fault with a minor normal component in most segments. Our study also infers the presence of a secondary structure, which is indicated to be a right-lateral strike-slip with a minor reverse component.