Aqaba Earthquake Research Articles

Discontinuous transtensional rupture during the Mw 7.2 1995 Gulf of Aqaba earthquake

The Gulf of Aqaba earthquake occurred on 22 November 1995 in the Northern Red Sea and is the largest instrumentally recorded earthquake in the region to date. The event was extensively studied during the initial years following its occurrence. However, it remained unclear which of the many faults in the gulf were activated during the earthquake. We present results from multi-array back projection that we use to inform Bayesian kinematic rupture models constrained by geodetic and teleseismic data. Our results indicate that most of the moment release was on the Aragonese fault via left-lateral strike slip and shallow normal faulting that may have been dynamically triggered by an early rupture phase on the Arnona fault. We also identified a predominantly normal fault-segment on the eastern shore of the gulf that was activated in the event. We dismiss the previously proposed hypothesis of a co-seismic sub-event on the western shore of the gulf and confirm that observed deformation can be rather attributed to post-seismic activity. In conclusion, the gulf shows many signs of active tectonic extension. Therefore, more events close to the shorelines are to be expected in the future and should be considered conducting infrastructure projects in the region.

Dynamic Source Parameters of Significant Earthquakes in the Gulf of Aqaba, Egypt

Several seismological and paloseismolgical studies and historical reports have indicated that Gulf of Aqaba is characterized by higher seismicity than any other seismogenic sources around Egypt. Accordingly, surrounding areas have been impacted by several destructive earthquakes (AD 1068, AD 1212, AD 1229, AD 1458, and AD 1995). Cities situated around the Gulf of Aqaba have experienced different damage levels due to historical and instrumental earthquakes resulting in considerable fatalities. The Aqaba earthquake which occurred on November 22, 1995 (Moment magnitude (Mw) = 7.3) was the largest recorded earthquake along with the Dead Sea Fault System, strongly felt at Eastern Mediterranean region. Many seismic sequences have ocuuerd in the Gulf of Aqaba in the last decades and some of them continued for almost two years. This paper applies a spectral decomposition method based on a reference site to correct the source spectra from the path and site effects by employing Iterative Least Square analysis. The obtained displacement source spectra are modulated with Brune’s omega square type spectrum. The dynamic earthquakes parameters are computed using the S-wave window for the significant Gulf of Aqaba earthquakes. 50 earthquakes have been used in this study with Ml 3.0 to 6. The calculated seismic moments range spans from 1.48E+19 to 2.193E+22 dyne-cm, and the corner frequency range spans from 4.1 to 8.5 Hz. The source radii span which range from 84.3 m to 173.4 meters. The observed stress drops vary from 0.3 to 371.7 megapascal (Mpa).

The Aqaba Earthquake, 22 November 1995 (7.3 Mw): insights on the seismicity and active faulting of Gulf of Aqaba

The Aqaba Earthquake, 22 November 1995 (7.3 Mw): insights on the seismicity and active faulting of Gulf of Aqaba

Numerical modelling of dynamic stability of RCC dam

Stability and stress analyses are the most important elements that require rigorous consideration in design of a dam structure. In the current research, dynamic structural stability of a roller-compacted-concrete (RCC) dam was performed. The RCC dam was modeled using the finite element method to investigate the stability against sliding and the structural stability of the body of the dam. The commercially available finite element software (SAP 2000) was used to analyze stresses in the body of the dam and foundation. A linear finite element dynamic analysis was performed. Response spectrum and time history methods were used with different earthquake loads. The response spectrum of the 1995 Aqaba earthquake and a representative elastic-spectrum with smooth plateau for both Operating Basis Earthquake (OBE) and Maximum Credible Earthquake (MCE) were used in this study. The analysis was carried out assuming that no slip will occur at the interface between the dam and the foundation. The greatest tension was found to develop in the rock adjacent to the toe of the upstream slope. The factor of safety against sliding along the entire base of the dam was found to be greater than 1 (FS>1), for both loading conditions.

Source parameters of the 27th of June 2015 Gulf of Aqaba earthquake

On the 27 June 2015, at 15:34:03 UTC, a moderate-sized earthquake of M w 5.0 occurred in the Gulf of Aqaba. Using teleseismic P waves, the focal mechanism of the mainshock was investigated by two techniques. The first technique used the polarities of the first P wave onsets, and the second technique was based on the normalized waveform modeling technique. The results showed that the extension stress has a NE orientation with a shallow southward plunge while the compression stress has a NW trend with a nearly shallow westward plunge, obtaining a strike-slip mechanism. This result agrees well with the typical consequence of crustal deformation resulting from the ongoing extensional to shear stress regime in the Gulf of Aqaba (NE-SW extension and NW-SE compression). The grid search method over a range of focal depths indicates an optimum solution at 15 ± 1 km. To identify the causative fault plane, the aftershock hypocenters were relocated using the local waveform data and the double-difference technique. Considering the fault trends, the spatial distribution of relocated aftershocks demarcated a NS-oriented causative fault, in consistence with one of the nodal planes of the focal mechanism solution, emphasizing the dominant stress regime in the region. Following the Brune model, the estimates of source parameters exhibited fault lengths of 0.29 ≤ L ≤ 2.48 km, moment magnitudes of 3.0 ≤ M w ≤ 5.0, and stress drops of 0.14 ≤ Δσ < 1.14 MPa, indicating a source scaling similar to the tectonic earthquakes related to plate boundaries.

Earthquake ground motion simulation at Zoser pyramid using the stochastic method: A step toward the preservation of an ancient Egyptian heritage

Strong ground shaking during earthquakes can greatly affect the ancient monuments and subsequently demolish the human heritage. On October 12th 1992, a moderate earthquake (Ms=5.8) shocked the greater Cairo area causing widespread damages. Unfortunately, the focus of that earthquake is located about 14km to the south of Zoser pyramid. After the earthquake, the Egyptian Supreme council of antiquities issued an alarm that Zoser pyramid is partially collapsed and international and national efforts are exerted to restore this important human heritage that was built about 4000years ago. Engineering and geophysical work is thus needed for the restoration process. The definition of the strong motion parameters is one of the required studies since seismically active zone is recorded in its near vicinity. The present study adopted the stochastic method to determine the peak ground motion (acceleration, velocity and displacement) for the three largest earthquakes recorded in the Egypt’s seismological history. These earthquakes are Shedwan earthquake with magnitude Ms=6.9, Aqaba earthquake with magnitude Mw=7.2 and Cairo (Dahshour earthquake) with magnitude Ms=5.8. The former two major earthquakes took place few hundred kilometers away. It is logic to have the predominant effects from the epicentral location of the Cairo earthquake; however, the authors wanted to test also the long period effects of the large distance earthquakes expected from the other two earthquakes under consideration. In addition, the dynamic site response was studied using the Horizontal to vertical spectral ratio (HVSR) technique. HVSR can provide information about the fundamental frequency successfully; however, the amplification estimation is not accepted. The result represented as either peak ground motion parameters or response spectra indicates that the effects from Cairo earthquake epicenter are the largest for all periods considered in the present study. The level of strong motion as indicated by peak ground acceleration reaches the value of 250gals which is considerably high. At the end, it is worth to mention that the information resulted from the present work may be useful for the planned restoration decision of the Zoser pyramid site.

Seismic response of a full-scale wind turbine tower using experimental and numerical modal analysis

Wind turbine technology has developed tremendously over the past years. In Egypt, the Zafarana wind farm is currently generating at a capacity of 517 MW, making it one of the largest onshore wind farms in the world. It is located in an active seismic zone along the west side of the Gulf of Suez. Accordingly, seismic risk assessment is demanded for studying the structural integrity of wind towers under expected seismic hazard events. In the context of ongoing joint Egypt–US research project “Seismic Risk Assessment of Wind Turbine Towers in Zafarana wind Farm Egypt” (Project ID: 4588), this paper describes the dynamic performance investigation of an existing Nordex N43 wind turbine tower. Both experimental and numerical work are illustrated explaining the methodology adopted to investigate the dynamic behavior of the tower under seismic load. Field dynamic testing of the full-scale tower was performed using ambient vibration techniques (AVT). Both frequency domain and time domain methods were utilized to identify the actual dynamic properties of the tower as built in the site. Mainly, the natural frequencies, their corresponding mode shapes and damping ratios of the tower were successfully identified using AVT. A vibration-based finite element model (FEM) was constructed using ANSYS V.12 software. The numerical and experimental results of modal analysis were both compared for matching purpose. Using different simulation considerations, the initial FEM was updated to finally match the experimental results with good agreement. Using the final updated FEM, the response of the tower under the AQABA earthquake excitation was investigated. Time history analysis was conducted to define the seismic response of the tower in terms of the structural stresses and displacements. This work is considered as one of the pioneer structural studies of the wind turbine towers in Egypt. Identification of the actual dynamic properties of the existing tower was successfully performed based on AVT. Using advanced techniques in both the field testing and the numerical investigations produced reliable FEM specific for the tested tower, which can be further used in more advanced structural investigations for improving the design of such special structures.

Updated Probabilistic Seismic‐Hazard Values for Egypt

Seismic hazard in terms of mean peak ground acceleration (PGA) and spectral acceleration (SA) values has been computed for Egypt using both historical and instrumental earthquake data. For this purpose, an updated earthquake catalog, spanning the time period from 2200 B.C. to 2013, has been compiled for Egypt as well as its surrounding regions and is prepared to be used in a new probabilistic seismic‐hazard assessment of Egypt. The earthquakes sizes were unified in terms of the moment magnitude scale. A new seismic source model for the seismic activity in and around Egypt, consisting of a total of 88 seismic zones (for shallow‐ and intermediate‐depth seismicity), was considered in this new assessment. The seismicity parameters have been specifically computed for 35 seismic sources covering the Egyptian territory and the Eastern Mediterranean region. A logic‐tree design was set up to consider the epistemic uncertainty in the Gutenberg–Richter b ‐value, maximum possible magnitude ( M max), and the selected ground‐motion prediction equations. Seismic‐hazard computations for rock‐site conditions with 10% and 5% probability of exceedance in 50 years were carried out. In addition, uniform hazard spectra for twelve, among the most important and populated cities in Egypt, are computed and compared with the most recent Egyptian building code values. It is interesting to highlight that the maximum hazard values are observed at the Gulf of Aqaba region, specifically around the epicentral location of the biggest Egyptian recorded earthquake of 22 November 1995 ( M w 7.2) Aqaba earthquake. The obtained seismic‐hazard values for Nuweiba city (located in this region) for mean PGA and SA (0.1 s) are 0.29 g and 0.74 g , respectively, for a return period of 475 years.

Seismological aspects of the 27 June 2015 Gulf of Aqaba earthquake and its sequence of aftershocks

On 27 June 2015, a moderate earthquake with magnitude Mb 5.2 struck the Gulf of Aqaba near Nuweiba City. This event was instrumentally recorded by the Egyptian National Seismic Network (ENSN) and many other international seismological centres. The event was felt in all the cities on the Gulf of Aqaba, as well as Suez City, Hurghada City, the greater Cairo Metropolitan Area, Israel, Jordan and the north-western part of Saudi Arabia. No casualties were reported, however. Approximately 95 aftershocks with magnitudes ranging from 0.7 to 4.2 were recorded by the ENSN following the mainshock. In the present study, the source characteristics of both the mainshock and the aftershocks were estimated using the near-source waveform data recorded by the very broadband stations of the ENSN, and these were validated by the P-wave polarity data from short period stations. Our analysis reveals that an estimated seismic moment of 0.762 × 1017 Nm was released, corresponding to a magnitude of Mw 5.2, a focal depth of 14 km, a fault radius of 0.72 km and a rupture area of approximately 1.65 km2. Monitoring the sequence of aftershocks reveals that they form a cluster around the mainshock and migrated downwards in focal depth towards the west. We compared the results we obtained with the published results from the international seismological centres. Our results are more realistic and accurate, in particular with respect to the epicenteral location, magnitude and fault plane solution which are in accordance with the hypocentre distribution of the aftershocks.

Recent evaluation of the assessment seismic hazards for Nuweiba, Gulf of Aqaba

The Gulf of Aqaba is considered seismically as one of the most active zones of the Dead Sea Transform region. The main shock of the 1995 Gulf of Aqaba earthquake sequence is considered as the largest shock in the (surface wave magnitude Ms = 7.2) since the sixteenth century. The present study is a trial to detect the probabilistic seismic hazard analysis (PSHA) for Nuweiba site. Data used for this study was a combination of both historical and recent instrumental data. Results of the hazard assessment, expressed as in the worst case scenario, reveal that Nuweiba is exposed to the occurrence of a maximum credible earthquake of magnitude $$ m_{{\max }} ~ = ~7.4 \pm 0.31 $$ , at hypocentral distance of 15.6 ± 10 km. For structure with the return period of 100 years, with a 90% probability of exceedance, the maximum expected earthquake magnitude (ML) is 5.9 in this lifetime. The possibility of the maximum peak ground acceleration at the Nuweiba site is 0.41 g. Results of the hazard assessment can be used as an input data to assess the seismic risk for site of interest.

Local Site Effects Estimated from Ambient Vibration Measurements at Aqaba City, Jordan

Ambient vibration measurements have been employed to estimate empirical site response functions in Aqaba City, Jordan. These measurements were made, using H/V technique, on nine selected sites that are representative for the different geological units beneath the city. The results show site–dependent variations in spectral amplitude, dominant frequency, and amplification level. The dominant frequency of the alluvial sediments shows a general decreasing in the NW direction from 1.8 to 0.3 Hz. No reliable difference in the levels of amplification that are in the range 1.8 to 2.1 was determined. The measurements at the highly fractured granitic site exhibit amplification of 1.8 at 3.9 Hz. The results indicate that the thickness of the loose sediments in western and northwestern part is much thicker than they are in eastern and northeastern parts. The shallow basement rocks in the eastern and northeastern shoulder of the city have direct effect on the measured peak frequency. The intensity and distribution of seismic destruction of the Gulf of Aqaba earthquake (November 22, 1995, Mw = 7.3) appear to correlate well with the dominant frequency as obtained in this study.

Another look at the 1993 and 1995 Gulf of Aqaba earthquakes from the analysis of teleseismic waveforms

In this work we estimated the source process and the source parameters of the 1993 and 1995 Gulf of Aqaba earthquakes. To investigate the source process of both events, we inverted the teleseismic P- and SH-waveform data using an iterative technique in which the rupture is modeled as a series of point source subevents with varying mechanisms. The main source process of the 1993 event can be explained by two subevents with essentially the same mechanism. These two subevents had different focal depths. The second subevent was about 5 s later than the first one and about 70% of the moment rate released with the second one. The total rupture duration time was about 12 s. Our solution for the 1995 Gulf of Aqaba earthquake indicated that the event consists of three subevents with various fault geometries and about 60% of the moment released by the second subevent. The first subevent occurred at a depth of 13 km, and was followed after 9 s by the second one at a depth of 11 km; the third subevent, at a depth of 9 km occurred 19 s after the second one. The total duration of the earthquake rupture process was about 18.7 s. The obtained mechanisms for the 1993 and 1995 Gulf of Aqaba earthquakes are well correlated with the structural setting of the Gulf of Aqaba.

The Syrian National Seismological Network (SNSN): Monitoring A Major Continental Transform Fault

The twenty-seven-station digital short-period (1 Hz) Syrian National Seismological Network utilizing a combination of radio-frequency (RF) and land-line (LL) telephone telemetry was installed and has been operational since 14 January 1995. Augmenting the seismic network is a twenty-station network of three-component digital accelerographs commissioned at the same time as the seismic network. The spatial distribution of both networks covers most of western Syria from north to south. The network's design criteria were to monitor all discernable earthquake activity along the Dead Sea fault system (DSFS) and its related branches in Syria and nearby Lebanon (Figure 1). This major fault system is characterized by relatively high seismic activity and, as the Program for Assessment and Mitigation of Earthquake Risk in the Arab Region (PAMERAR) initiative proposed in 1981 concluded, poses a significant seismic hazard to the densely populated areas surrounding it. The most recent and truly devastating large earthquake (deaths estimated at 20,000) along this fault system occurred in the Bekaa Valley within the large restraining bend on 25 November 1759 and had an estimated magnitude of greater than Ms 7.3 (Ambraseys and Barazangi, 1989). The Syrian territory has been affected in the past by many large earthquakes that occurred along the DSFS. During the last millennium, between 1022 and 1872, at least ten large earthquakes occurred in this zone (Sbeinati et al. , 1997), as did the recent 1995 Ms 7.3 Aqaba earthquake, which may have remotely triggered an earthquake swarm in southwestern Syria (Mohamad et al. , 2000). Figure 1 shows a plot of the most destructive historical earthquakes in Syria in addition to the 1995 Aqaba event. Some of the historic events were larger than Ms 7.3 (Ambraseys and Barazangi, 1989). In 1985 the General Establishment of Geology and Mineral Resources (GEGMR), …

Sources of the large A.D. 1202 and 1759 Near East earthquakes

Research Article| July 01, 2005 Sources of the large A.D. 1202 and 1759 Near East earthquakes M. Daëron; M. Daëron 1Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France Search for other works by this author on: GSW Google Scholar Y. Klinger; Y. Klinger 2 Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France Search for other works by this author on: GSW Google Scholar P. Tapponnier; P. Tapponnier 2 Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France Search for other works by this author on: GSW Google Scholar A. Elias; A. Elias 3Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France, and National Council for Scientific Research, P.O. Box 165432, Ashrafieh, 1100-2040 Beirut, Lebanon Search for other works by this author on: GSW Google Scholar E. Jacques; E. Jacques 4Ecole et Observatoire des Sciences de la Terre de Strasbourg, 5 rue René Descartes, F-67084 Strasbourg, France Search for other works by this author on: GSW Google Scholar A. Sursock A. Sursock 5National Council for Scientific Research, P.O. Box 11-8281, Riad El-Solh, 1107 2260 Beirut, Lebanon Search for other works by this author on: GSW Google Scholar Author and Article Information M. Daëron 1Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France Y. Klinger 2 Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France P. Tapponnier 2 Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France A. Elias 3Institut de Physique du Globe de Paris, UMR 7578, 4 place Jussieu, Boîte 89, 75252 Paris, France, and National Council for Scientific Research, P.O. Box 165432, Ashrafieh, 1100-2040 Beirut, Lebanon E. Jacques 4Ecole et Observatoire des Sciences de la Terre de Strasbourg, 5 rue René Descartes, F-67084 Strasbourg, France A. Sursock 5National Council for Scientific Research, P.O. Box 11-8281, Riad El-Solh, 1107 2260 Beirut, Lebanon Publisher: Geological Society of America Received: 05 Nov 2004 Revision Received: 26 Jan 2005 Accepted: 05 Feb 2005 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2005) 33 (7): 529–532. https://doi.org/10.1130/G21352.1 Article history Received: 05 Nov 2004 Revision Received: 26 Jan 2005 Accepted: 05 Feb 2005 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. Daëron, Y. Klinger, P. Tapponnier, A. Elias, E. Jacques, A. Sursock; Sources of the large A.D. 1202 and 1759 Near East earthquakes. Geology 2005;; 33 (7): 529–532. doi: https://doi.org/10.1130/G21352.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The sources of the May 1202 and November 1759, M 7.5 Near East earthquakes remain controversial, because their macroseismal areas coincide, straddling subparallel active faults in the Lebanese restraining bend. Paleoseismic trenching in the Yammoûneh basin yields unambiguous evidence both for slip on the Yammoû neh fault in the twelfth–thirteenth centuries and for the lack of a posterior event. This conclusion is supported by comparing the freshest visible fault scarps, which imply more recent slip on the Râchaïya-Serghaya system than on the Yammoûneh fault. Our results suggest that the recurrence of an A.D. 1202–type earthquake might be due this century, as part of a sequence similar to that of A.D. 1033–1202, possibly heralded by the occurrence of the 1995 Mw 7.3 Aqaba earthquake. The seismic behavior of the Levant fault might thus be characterized by millennial periods of quiescence, separated by clusters of large earthquakes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Seismic observations of the 22/11/1995 Gulf of Aqaba earthquake sequence

We analyzed the aftershock sequence of the Gulf of Aqaba earthquake recorded by short period and broad band stations between November 1995 and December 1996. The seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens. Most of the aftershock activity is concentrated north of the main shock in the Aragonese and Eilat basins, while the activity is diffused south of the main shock in the Dakar and Tiran basins. Most of the moderate to strong aftershocks of the whole aftershock sequence occurred in the Aragonese basin, mainly in the first 100 days following the main shock. The Eilat basin is characterized by a larger number of aftershocks composed mainly of small-magnitude implying a slower decay rate. Assuming a detection level of M L=3.2 we obtain b-values of 1.01, 1.15, and 0.89 for the whole Gulf of Aqaba, and Eilat and Aragonese basins, respectively, in good agreement with recent studies of the Dead Sea fault. Following Omori's law, we obtained a decay parameter of 0.94, 0.88, and 0.96 for the aftershock sequences in the whole Gulf of Aqaba, and the Eilat and Aragonese basins, respectively, correlative with regions of low heat flow. For 1630 events in the local magnitude range of 0.6≤ M L≤6.2 we found seismic moment estimates, M 0, of 5×10 18≤ M 0≤7.7×10 26 dyn cm, and Brune stress drop estimates, Δ σ, between 1 and 200 bars, with a characteristic value of 90 bars in the Eilat and Aragonese basins for M 0>5×10 21 dyn cm. These characteristics are comparable to those for events occurring on the main Dead Sea–Jordan fault. Most of the moment release in the basins occurred shortly after the occurrence of the main shock. The total moment release in the Eilat and Aragonese basins is only a fraction of the moment release of the main shock suggesting an almost complete stress release.

Source mechanism of the 22/11/1995 Gulf of Aqaba earthquake and its aftershock sequence

The Gulf of Aqaba earthquake occurred on 22/11/1995 with M W = 7.2 and was the largest event to occur along the Dead Sea Transform in at least a century. We determined the source mechanism of the event based on the inversion of the P and SH waveforms observed by teleseismic stations. Our solution consists of 2 similar subevents, where the first exhibits a left-lateral strike-slip motion with a normal component and the second subevent shows an almost pure left-lateral strike-slip motion along the gulf major fault system. The total seismic moment is 7.7 × 1026 dyne-cm, with source duration of 15 seconds. The aftershock sequence was recorded by the regional broad band stations BGIO and JER, of the Israel Seismic Network, and KEG, of the MEDNET regional network for earthquakeswith M W > 4.0. Aftershock epicenter seems to cluster mainly in the Eilat basin and the Aragonese basin. The dominant mechanism indicates left-lateral strike slip motion along the gulf trend, similar to the mainshock.

Active displacement field in the Suez–Sinai area: the role of postseismic deformation

By means of a spherical viscoelastic model of co- and postseismic deformation we compute the postseismic displacement associated with the November, 1995, M w=7.2, Aqaba (Jordan) earthquake. We compare our results with the observational data obtained by a GPS campaign performed in a wide portion of Sinai between November 1997 and May 1998. Though the original purpose of the campaign was to explain the tectonic features of the region, the displacement values deduced from the GPS observations are hardly reconcilable with any of the proposed tectonic models of Sinai. Our hypothesis is that the detected deformation field could be due more to the postseismic relaxation following the Aqaba earthquake rather than to tectonic movements. Our results show that both GPS observational data and the postseismic simulations predict a compressional regime in the Gulf of Suez though the contraction detected by GPS is generally larger. The best agreement with the data is obtained for an asthenospheric and lower crust viscosity of 10 18 Pa s and an absence of aseismic afterslip on the fault plane. We conclude that the contribution coming from the postseismic viscoelastic relaxation of the ductile shallow layers following the 1995 Aqaba earthquake is likely to play an important role in determining the present deformation field in Sinai. The transient postseismic relaxation seems to play a more important role than the secular tectonic deformation.

Teleseismic inversion for the second-degree moments of earthquake space-time distributions

Determining detailed descriptions of the space–time distribution of an earthquake's rupture using only teleseismic data is often a difficult and non unique process. However, a description of an earthquake that goes beyond a point source is often needed for many seismotectonic problems. We have developed a method that inverts measurements of the shifts in traveltime and amplitude of various seismic phases at global stations for the second degree polynomial moments of an event's space–time distribution. Our values for the second moments of the 1995 Mw 8.0 Jalisco, Mexico, thrust event correspond to a characteristic rupture length of 121±10 km along strike, a characteristic rupture width of 76±11 km downdip, a characteristic duration of 29±2 s, and a direction of rupture propagation along the strike of the subduction zone to the NW. For the 1995 Mw 7.2 Gulf of Aqaba earthquake, our estimates of the second moments correspond to a characteristic rupture length of 53±2 km, a characteristic duration of 12±1 s, and rupture propagation to the NE along the strike of the Dead Sea Transform. Our estimates of the first and second moments agree well with values from local seismic and geodetic networks. For both the Jalisco and Aqaba events, we are able to resolve the fault plane ambiguity associated with the events' moment tensors using our estimates of the second spatial moment.

Co‐seismic deformation during the Mw7.3 Aqaba Earthquake (1995) from ERS‐SAR interferometry

The Mw7.3 1995 Aqaba earthquake is the largest instrumental earthquake along the Dead Sea Fault. We complement previous seismological studies by analyzing co‐seismic ground displacement from differential interferometry computed from ERS images spanning 3 different areas. They are compared with a synthetic model derived from seismological study. Only far‐field deformation related to the main sub‐event could be revealed because the near‐field area lies within the gulf. The interferometric data imply a 56 km long and 10 km wide fault segment, connecting the Elat Deep to the Aragonese Deep, which strikes N195°E and dips 65° to the west, with 2.1 m left‐lateral slip and a 15.5° rake indicating a slight normal component. The geodetic moment compares well with the seismic moment.

Ground motion characteristics of the November 1995 Aqaba earthquake

The paper documents the main characteristics of the seismic activity in Jordan's southern port city of Aqaba associated with the earthquake swarm in November 1995. A review is made of the seismicity of the Aqaba region. Damage due to the 22 November earthquake is reported and so are the measurements of this activity and its aftershocks. Durations and frequency contents are computed and analyzed. Power spectral densities are generated. The strong influence of magnitude on frequency content is noted and discussed. The amplification of soil to the rock motion is investigated both based on recorded data and using an analytical approach. The computer program SHAKE91 is used to study the soil response of the Aqaba profiles using a previous record on rock for a 1979 earthquake on the same fault. Correlation is found between recorded data and the theoretical model for soil amplification. Recommendations are made for designers including design response spectra for two soil profiles in Aqaba.