RSS 1.0Qademah Fault Project
Recent Submissions
-
Imaging near-surface heterogeneities by natural migration of surface waves(SEG Technical Program Expanded Abstracts 2016, Society of Exploration Geophysicists, 2016-09) [Conference Paper]We demonstrate that near-surface heterogeneities can be imaged by natural migration of backscattered surface waves in common shot gathers. No velocity model is required because the data are migrated onto surface points with the virtual Green's functions computed from the shot gathers. Migrating shot gathers recorded by 2D and 3D land surveys validates the effectiveness of detecting nearsurface heterogeneities by natural migration. The implication is that more accurate hazard maps can be created by migrating surface waves in land surveys.
-
Skeletonized inversion of surface wave: Active source versus controlled noise comparison(Interpretation, Society of Exploration Geophysicists, 2016-07-14) [Article]We have developed a skeletonized inversion method that inverts the S-wave velocity distribution from surface-wave dispersion curves. Instead of attempting to fit every wiggle in the surface waves with predicted data, it only inverts the picked dispersion curve, thereby mitigating the problem of getting stuck in a local minimum. We have applied this method to a synthetic model and seismic field data from Qademah fault, located at the western side of Saudi Arabia. For comparison, we have performed dispersion analysis for an active and controlled noise source seismic data that had some receivers in common with the passive array. The active and passive data show good agreement in the dispersive characteristics. Our results demonstrated that skeletonized inversion can obtain reliable 1D and 2D S-wave velocity models for our geologic setting. A limitation is that we need to build layered initial model to calculate the Jacobian matrix, which is time consuming.
-
Geotechnical Parameters from Seismic Measurements: Two Field Examples from Egypt and Saudi Arabia(Journal of Environmental and Engineering Geophysics, Environmental and Engineering Geophysical Society, 2016-03-18) [Article]© 2016 EEGS. Geotechnical parameters were used to determine subsurface rock quality for construction purposes. We summarize the mathematical relationships used to calculate the geotechnical parameters from P- and S-wave velocities and density values. These relationships are applied to two field examples; the first is a regional seismic study in Egypt and the second is a 2-D seismic profile recorded in Saudi Arabia. Results from both field examples are used to determine the subsurface rock quality and locate zones that should be avoided during construction. We suggest combining all geotechnical parameters into one map using a normalized-weighted relation, which helps to locate the zones with high versus low rock quality for engineering purposes.
-
Qademah Fault Seismic Data Set - Northern Part(KAUST Research Repository, 2015-01) [Dataset]Objective: Is the Qademah fault that was detected in 2010 the main fault? We collected a long 2D profile, 526 m, where the fault that was detected in 2010 is at around 300 m. Layout: We collected 264 CSGs, each has 264 receivers. The shot and receiver interval is 2 m. We also collected an extra 48 CSGs with offset = 528 to 622 m with shot interval = 2 m. The receivers are the same as the main survey.
-
Iterative supervirtual refraction interferometry(GEOPHYSICS, Society of Exploration Geophysicists, 2014-05-02) [Article]In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.
-
Qademah Fault Artificial Ambient Noise Test(KAUST Research Repository, 2014) [Dataset]This data set was collected on 7 Dec. 2014 by Sherif and Abdullah. The receiver layout is the same as that of the passive data test at the same location, which is described as follow: 288 receivers are used and arranged as follow - 12 lines, cross-line offset = 10 m - 24 receiver in each line, inline offset = 5 m - Additional 24 receivers are placed at line # 6, where the receiver interval is decreased to 2.5 m. Data Recording: We start recording at 10:10 am and stop recording at 11:25 am. Each record has total of 20 s, with time interval of 0.004 ms and around 2 s overlap between each two successive files. Source: We used a piece of wood attached to a pick-up truck to create the noise; we drove around the array of receivers in a rectangle-shape route during the recording time.
-
Qademah Fault 3D Survey(KAUST Research Repository, 2014) [Dataset]Objective: Collect 3D seismic data at Qademah Fault location to 1. 3D traveltime tomography 2. 3D surface wave migration 3. 3D phase velocity 4. Possible reflection processing Acquisition Date: 26 – 28 September 2014 Acquisition Team: Sherif, Kai, Mrinal, Bowen, Ahmed Acquisition Layout: We used 288 receiver arranged in 12 parallel lines, each line has 24 receiver. Inline offset is 5 m and crossline offset is 10 m. One shot is fired at each receiver location. We use the 40 kgm weight drop as seismic source, with 8 to 15 stacks at each shot location.
-
Qademah Fault Passive Data(KAUST Research Repository, 2014) [Dataset]OBJECTIVE: In this field trip we collect passive data to 1. Convert passive to surface waves 2. Locate Qademah fault using surface wave migration INTRODUCTION: In this field trip we collected passive data for several days. This data will be used to find the surface waves using interferometry and then compared to active-source seismic data collected at the same location. A total of 288 receivers are used. A 3D layout with 5 m inline intervals and 10 m cross line intervals is used, where we used 12 lines with 24 receivers at each line. You will need to download the file (rec_times.mat), it contains important information about 1. Field record no 2. Record day 3. Record month 4. Record hour 5. Record minute 6. Record second 7. Record length P.S. 1. All files are converted from original format (SEG-2) to matlab format P.S. 2. Overlaps between records (10 to 1.5 sec.) are already removed from these files
