National Center for Earthquakes and Volcanoes

Jeddah, Saudi Arabia

National Center for Earthquakes and Volcanoes

Jeddah, Saudi Arabia
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Zahran H.M.,National Center for Earthquakes and Volcanoes | Sokolov V.,National Center for Earthquakes and Volcanoes | Youssef S.E.H.,National Center for Earthquakes and Volcanoes | Youssef S.E.H.,National Research Institute for Astronomy and Geophysics | Alraddadi W.W.,National Center for Earthquakes and Volcanoes
Soil Dynamics and Earthquake Engineering | Year: 2015

We create and test a framework for probabilistic seismic hazard assessment for the Kingdom of Saudi Arabia using Monte Carlo simulation, recently developed models of seismic source zones and modern ground-motion prediction equations (GMPE). A generalized seismic source model containing 43 zones has been compiled and seven GMPEs were selected. The assessment was performed on the basis of 100 synthetic seismic sub-catalogs with duration 10,000 years each. The hazard curves were calculated for the nodes of 0.25°×0.25° grid and the hazard maps were created in terms of PGA, PGV and seismic intensity for rock sites. Preliminary sensitivity analysis was performed to determine the importance of the input parameters and the level of uncertainty introduced by the parameters. The developed framework and the results of PSHA provide a benchmark for the comprehensive seismic hazard and seismic risk analysis and up-to-date seismic hazard maps for the Kingdom of Saudi Arabia. © 2015 Elsevier Ltd.


Al-Lazki A.I.,Sultan Qaboos University | Al-Lazki A.I.,Petroleum Development Oman | Al-Damegh K.S.,Astronomy and Geophysics Research Institute | El-Hadidy S.Y.,National Center for Earthquakes and Volcanoes | And 2 more authors.
Geological Society Special Publication | Year: 2014

We use Pn-tomography to map lithospheric mantle velocity and anisotropy at the Arabia-Eurasia plate boundary, namely Makran and Zagros. We use catalogue events recorded by Oman, UAE, Saudi Arabia and Iran networks, the International Seismological Centre and the National Earthquake Information Center. Events of 1.8-16 degree distances were used for this Pn-tomography. In this study we show that the northeastern Arabia plate is characterized by cold and stable lithospheric mantle. Contrastingly, Eurasia is underlain by hot unstable lithospheric mantle. The Arabia-Eurasia lithospheric suture follows the Zagros collision surface suture within c. 70 km lateral proximity. At the southernmost Zagros collision, the Arabia lithosphere is inferred to extend further NE beneath Lut Block. This may be indicative of extended subduction of Arabia beneath Eurasia in southernmost Zagros. We find that eastern Makran shows typical subduction characteristics, with inferred oceanic lithosphere underlying the eastern Oman Sea and hot unstable lithospheric mantle below overriding Helmand Block. Contrastingly, the western Makran subduction zone including Arabia and Eurasia continental sides is underlain by a low-Pn-velocity anomaly, indicative of hot unstable lithospheric mantle. Surface evidence show that western, southern and eastern boundaries of western Makran low-Pn-velocity anomaly may represent a Late Neogene reactivated Precambrian terrane boundary in north Oman. © The Geological Society of London 2014.


Sokolov V.,Karlsruhe Institute of Technology | Sokolov V.,National Center for Earthquakes and Volcanoes | Ismail-Zadeh A.,Karlsruhe Institute of Technology | Ismail-Zadeh A.,CNRS Paris Institute of Global Physics
Tectonophysics | Year: 2015

We present a new approach to assessment of regional seismic hazard, which accounts for observed (instrumentally recorded and historic) earthquakes, as well as for seismic events simulated for a significantly longer period of time than that of observations. We apply this approach to probabilistic seismic hazard analysis (PSHA) for the Tibet-Himalayan region. The large magnitude synthetic events, which are consistent with the geophysical and geodetic data, together with the observed earthquakes are employed for the Monte-Carlo PSHA. Earthquake scenarios for hazard assessment are generated stochastically to sample the magnitude and spatial distribution of seismicity, as well as the distribution of ground motion for each seismic event. The peak ground acceleration values, which are estimated for the return period of 475 yr, show that the hazard level associated with large events in the Tibet-Himalayan region significantly increases if the long record of simulated seismicity is considered in the PSHA. The magnitude and the source location of the 2008 Wenchuan M= 7.9 earthquake are among the range of those described by the seismic source model accepted in our analysis. We analyze the relationship between the ground motion data obtained in the earthquake's epicentral area and the obtained PSHA estimations using a deaggregation technique. The proposed approach provides a better understanding of ground shaking due to possible large-magnitude events and could be useful for risk assessment, earthquake engineering purposes, and emergency planning. © 2015 Elsevier B.V.


Sokolov V.,Karlsruhe Institute of Technology | Sokolov V.,National Center for Earthquakes and Volcanoes | Ismail-Zadeh A.,Karlsruhe Institute of Technology | Ismail-Zadeh A.,Russian Academy of Sciences | Ismail-Zadeh A.,CNRS Paris Institute of Global Physics
Tectonophysics | Year: 2015

We present a new approach to assessment of regional seismic hazard, which accounts for observed (instrumentally recorded and historic) earthquakes, as well as for seismic events simulated for a significantly longer period of time than that of observations. We apply this approach to probabilistic seismic hazard analysis (PSHA) for the Tibet-Himalayan region. The large magnitude synthetic events, which are consistent with the geophysical and geodetic data, together with the observed earthquakes are employed for the Monte-Carlo PSHA. Earthquake scenarios for hazard assessment are generated stochastically to sample the magnitude and spatial distribution of seismicity, as well as the distribution of ground motion for each seismic event. The peak ground acceleration values, which are estimated for the return period of 475. yr, show that the hazard level associated with large events in the Tibet-Himalayan region significantly increases if the long record of simulated seismicity is considered in the PSHA. The magnitude and the source location of the 2008 Wenchuan M = 7.9 earthquake are among the range of those described by the seismic source model accepted in our analysis. We analyze the relationship between the ground motion data obtained in the earthquake's epicentral area and the obtained PSHA estimations using a deaggregation technique. The proposed approach provides a better understanding of ground shaking due to possible large-magnitude events and could be useful for risk assessment, earthquake engineering purposes, and emergency planning. © 2015 Elsevier B.V.


Sokolov V.,Karlsruhe Institute of Technology | Sokolov V.,National Center for Earthquakes and Volcanoes | Wenzel F.,Karlsruhe Institute of Technology
Bulletin of Earthquake Engineering | Year: 2015

The results of classical probabilistic seismic hazard analysis (PSHA) contain no information about simultaneous ground motions at different sites during a particular earthquake. Seismic risk analysis for distributed critical structures requires estimates of the level of earthquake shaking that are likely to occur concurrently at multiple locations: whether the vulnerable elements of a lifeline system are likely to be simultaneously affected by shaking of sufficient strength to disable them and whether the shaking at any one of critical points may be sufficient to cause failure of the whole system. While the analysis of lifeline performance requires multiple-location estimations, the sparsely located elements of a network or critical facilities are designed on the basis of point-wise PSHA. In this paper we study specific features of multiple-location PSHA, as compared with the classical point-wise PSHA, using Monte Carlo simulations. We analyze the level of ground motion (PGA) that will be exceeded at any site inside a particular area or at several sites simultaneously with reference annual probability. The analysis has been performed for regions of Western and South-Western Germany, Northern and Eastern Taiwan, which represent different levels of seismicity (low, moderate and high, respectively). The relationship between the multiple-location and point-wise estimations are analyzed and quantified. Results of the study may be used to decide whether it may be possible to utilize the procedure of point-wise PSHA in particular cases of multiple-location PSHA, i.e. for assessment of maximum level of ground motion among several sites, or for estimation a reasonable lower safety level when considering simultaneous exceedances. © 2014, Springer Science+Business Media Dordrecht.


Sokolov V.,National Center for Earthquakes and Volcanoes | Ismail-Zadeh A.,Karlsruhe Institute of Technology
Bulletin of the Seismological Society of America | Year: 2016

We analyze specific features of multiple-site (MS) probabilistic seismic-hazard assessment (PSHA), that is, the annual rate of ground-motion level exceedance in at least one of several sites of interest located within a defined area or along a linear extended object. The relation between MS hazard estimates and strong ground motion data obtained during large earthquakes is discussed in the cases of the 1999 Chi-Chi Mw 7.6 and the 2008 Wenchuan Mw 7.9 earthquakes. The strong-motion records obtained in the epicentral zones may be considered as examples of the ground motion exceeding the design level estimated using the conventional pointwise (PW) PSHA. We show that the MS-PSHA, when being performed for the 475 yr standard return period, provides reasonable estimations of the intensity level that may occur during the earthquakes, parameters of which are close to the parameters of events with maximum possible magnitude accepted in PSHA for the regions. The MS-PSHA efficiency is discussed with respect to (1) evaluation of the performance of probabilistic seismic-hazard maps and (2) application of the MS hazard estimates as a basis for design loads. Based on the results of this work, we propose a multilevel approach to PSHA considering the fixed reference probability of exceedance (e.g., 10% in 50 yrs): (1) a standard PW-PSHA, to be performed in a seismic-prone region (first level), and (2) this analysis should be supplemented by an MS-PSHA for urban and industrial areas or for zones of a particular economic and social importance (second level). © 2016 Seismological Society of America. All rights reserved.


Pallister J.S.,U.S. Geological Survey | McCausland W.A.,U.S. Geological Survey | Jonsson S.,King Abdullah University of Science and Technology | Lu Z.,U.S. Geological Survey | And 7 more authors.
Nature Geoscience | Year: 2010

The extensive harrat lava province of Arabia formed during the past 30 million years in response to Red Sea rifting and mantle upwelling. The area was regarded as seismically quiet, but between April and June 2009 a swarm of more than 30,000 earthquakes struck one of the lava fields in the province, Harrat Lunayyir, northwest Saudi Arabia. Concerned that larger damaging earthquakes might occur, the Saudi Arabian government evacuated 40,000 people from the region. Here we use geologic, geodetic and seismic data to show that the earthquake swarm resulted from magmatic dyke intrusion. We document a surface fault rupture that is 8 km long with 91 cm of offset. Surface deformation is best modelled by the shallow intrusion of a north-west trending dyke that is about 10 km long. Seismic waves generated during the earthquakes exhibit overlapping very low- and high-frequency components. We interpret the low frequencies to represent intrusion of magma and the high frequencies to represent fracturing of the crystalline basement rocks. Rather than extension being accommodated entirely by the central Red Sea rift axis, we suggest that the broad deformation observed in Harrat Lunayyir indicates that rift margins can remain as active sites of extension throughout rifting. Our analyses allowed us to forecast the likelihood of a future eruption or large earthquake in the region and informed the decisions made by the Saudi Arabian government to return the evacuees. © 2010 Macmillan Publishers Limited. All rights reserved.


Kereszturi G.,Massey University | Nemeth K.,Massey University | Moufti M.R.,King Abdulaziz University | Cappello A.,Italian National Institute of Geophysics and Volcanology | And 6 more authors.
Journal of Volcanology and Geothermal Research | Year: 2016

Lava flow hazard modelling requires detailed geological mapping, and a good understanding of emplacement settings and the processes involved in the formation of lava flows. Harrat Rahat, Kingdom of Saudi Arabia, is a large volcanic field, comprising about 1000 predominantly small-volume volcanoes most of which have emitted lava flows of various lengths. A few eruptions took place in this area during the Holocene, and they were located in the northern extreme of the Harrat Rahat, a close proximity to critical infrastructure and population living in Al-Madinah City. In the present study, we combined field work, high resolution digital topography and morphometric analysis to infer the emplacement history of the last historical event in the region represented by the 1256AD Al-Madinah lava flow field. These data were also used to simulate 1256AD-type lava flows in the Harrat Rahat by the MAGFLOW lava flow emplacement model, which is able to relate the flow evolution to eruption conditions. The 1256AD lava flow field extent was mapped at a scale of 1:1000 from a high resolution (0.5m) Light Detection And Ranging (LiDAR) Digital Terrain Model (DTM), aerial photos with field support. The bulk volume of the lava flow field was estimated at 0.4km3, while the source volume represented by seven scoria cone was estimated at 0.023km3. The lava flow covered an area of 60km2 and reached a maximum length of 23.4km. The lava flow field comprises about 20.9% of pahoehoe, 73.8% of 'a'a, and 5.3% of late-stage outbreaks. Our field observation, also suggests that the lava flows of the Harrat Rahat region are mainly core-dominated and that they formed large lava flow fields by amalgamation of many single channels. These channels mitigated downslope by topography-lava flow and channel-channel interactions, highlighting this typical process that needs to be considered in the volcanic hazard assessment in the region. A series of numerical lava flow simulations was carried out using a range of water content (0.1-1wt.%), solidification temperature (800-600°C) and effusion curves (simple and complex curves). These simulations revealed that the MAGFLOW code is sensitive to the changes of water content of the erupting lava magma, while it is less sensitive to solidification temperature and the changes of the shape of effusion curve. The advance rate of the simulated lava flows changed from 0.01 to 0.22km/h. Using data and observations from the youngest volcanic event of the Harrat Rahat as input parameters to MAGFLOW code, it is possible to provide quantitative limits on this type of hazard. © 2015 Elsevier B.V.


Tang Z.,King Abdullah University of Science and Technology | Julia J.,Federal University of Rio Grande do Norte | Zahran H.,National Center for Earthquakes and Volcanoes | Mai P.M.,King Abdullah University of Science and Technology
Tectonophysics | Year: 2016

We investigate the lithospheric shear-wave velocity structure of Saudi Arabia by conducting H-κ stacking analysis and jointly inverting teleseismic P-receiver functions and fundamental-mode Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). The study region, the Arabian plate, is traditionally divided into the western Arabian shield and the eastern Arabian platform: The Arabian shield itself is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (locally known as harrats). The Arabian platform is primarily covered by 8 to 10 km of Paleozoic, Mesozoic and Cenozoic sedimentary rocks. Our results reveal high Vp/Vs ratios in the region of Harrat Lunayyir, which are interpreted as solidified magma intrusions from old magmatic episodes in the shield. Our results also indicate slow velocities and large upper mantle lid temperatures below the southern and northern tips of the Arabian shield, when compared with the values obtained for the central shield. We argue that our inferred patterns of lid velocity and temperature are due to heating by thermal conduction from the Afar plume (and, possibly, the Jordan plume), and that volcanism in western Arabia may result from small-scale adiabatic ascent of magma diapirs. © 2016 The Authors.

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