The anti-correlation method for removing harmonic distortion in vibroseis slip-sweep data

The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group＇s sweep to terminate. The cycle time can be reduced drastically and hence the production efficiency can be increased significantly but harmonic distortion of one sweep will leak into the record of the other sweep. In this paper, we propose an anti-correlation method for removing harmonic distortion in vibroseis data. This method is based on decomposition of the ground force signal into fundamental and harmonic components. Then the corresponding anti-correlation operator can be computed to estimate the energy of each harmonic after correlating the vibroseis data with the corresponding harmonic component. Finally, the vibroseis harmonic noise to be removed can be obtained by subtracting the extracted harmonic noise from the traces of the previous group＇s sweep. The advantage of the proposed method is that it can process both uncorrelated and correlated vibroseis seismic data. Moreover, the algorithm is simple, stable, and computationally fast. Especially, the significant contribution of this method is a considerable reduction in the harmonic without any alteration of the desired signals. The method was tested on both synthetic and field data sets to validate the good harmonic noise suppression results.

Structural Development of Northwest Saudi Arabia Using Aeromagnetic and Seismological Data

High resolution aeromagnetic and seismological data constrained by field-based structural investigations have been used to map and delineate the structural elements that affected and shaped the Midyan area in the northwest part of Saudi Arabia. The area was divided into four major domains defined by NNE, NNW, NW and ENE trending faults identified by trends, patterns and intensity of magnetic anomalies. The ENE trending left-lateral strike-slip faults intersected by NNE trending faults are the predominant tectonic features in the Gulf of Aqaba coastal area and stop at the boundary of a central domain characterized by complexity in the pattern and intensity of magnetic anomalies, that may be attributed to heterogeneity of basement rocks containing complex igneous rock suites including diorite, gabbro, ultramafic and alkali granitic rocks. This domain is characterized by the presence of narrow linear magnetic anomalies that extend for kilometers in an NNW direction, indicating dikes intruded through NNW trending faults. These dikes become WNW-oriented near their northern termination by transfer of movement to WNW-oriented faults marking the northern termination of the Red Sea rift. It is believed that this fault zone is still experiencing neotectonic activity, as evident from recorded seismicity. The aeromagnetic structural resuits coincide with fault plane solutions for the largest earthquakes, confirming aeromagnetic interpreted trends and illustrating mixed mechanisms between extensional and strike-slip faulting. Thus the study area displays different mechanisms associated with different tectonic trends which show clearly in the structural patterns of the area.

Prediction of the shear wave velocity Vs from CPT and DMT at research sites

The paper examines the correlations to obtain rough estimates of the shear wave velocity Vs from non- seismic dilatometer tests （DMT） and cone penetration tests （CPT）. While the direct measurement of Vs is obviously preferable, these correlations may turn out useful in various circumstances. The experimental results at six international research sites suggest that the DMT predictions of Vs from the parameters ID （material index）, KD （horizontal stress index）, MDMT （constrained modulus） are more reliable and consistent than the CPT predictions from qc （cone resistance）, presumably because of the availability, by DMT, of the stress history index KD.

DISCOVERY OF HOLOTRICHIA AND OTHER INSECT FOSSILS IN THE LOWER PLEISTOCENE OF BEIJING

In the summer of 1979 we found some insect fossils in the drill cores near the River Wenyu, in the southwest of County Shunyi, Boijing. They were discovered in the silt clay of Xiadian Formation, lower Pleistocene.These insect fossils are of Asilldae (gen. et sp. indet.), Harpalidae (gen. et sp. indet.), Lyetidae (gen. et sp. indet.) and Melolonthinae, Subgen. Holotrichia Reitter. The latter is a new species of the subgenus Holotrichia (s. str.) under the name of Holotrichia (s. str.) beijingensis Wang sp. nov.. It has the same eharacteristics with subgenus Holotrichia as well as the modern Holotrichia (s. str.) szechuanensis in spite of some difference.