Research on Technology and Application of Buried Faults Identification in Urban Underground Space

With theurbanization rate's rising and three-dimensional expansion and development of urban, the identification of underground buried faults has become the key factor of earthquake risk in urban underground space and surface area. As a typical method of detecting blind faults in underground space, shallow seismic prospecting technology plays an important role in judging and avoiding potential risks such as underground faults in the process of urban expansion and site selection. In this paper, shallow seismic prospecting technology is adopted, and optimized processing technologies such as parameter test, tomographic correction, pre-stack denoising, fidelity and consistency processing, correction iteration, migration imaging, and time-depth relationship deduction are adopted. Underground faults are identified and interpreted in the studied urban area, and fault risk assessment is carried out based on fault characteristics, scale, distribution and overlying strata, thus providing suggestions for regional pattern and construction of urban planning.

APPLICATION OF SURFACE CONSISTENT DECONVOLUTION METHOD ON 2D SHALLOW SEISMIC DATA IN WAIPOGA WATER, PAPUA

Data seismik yang dihasilkan saat akuisisi mengandung wavelet yang kompleks dan noise seperti multiple yang mengakibatkan menurunnya resolusi temporal penampang seismik. Penelitian ini bertujuan untuk membandingkan penerapan metode Surface Consistent Deconvolution dan dekonvolusi prediktif dalam meningkatkan resolusi temporal penampang seismik pada data seismik laut dangkal 2D lintasan C12, C21 dan L18 di Perairan Waipoga, Papua. Penampang seismik yang dihasilkan pada penelitian ini menunjukkan bahwa penerapan metode dekonvolusi prediktif maupun Surface Consistent Deconvolution dapat menghilangkan short-period multiple yang terdapat pada penampang seismik. Metode Surface Consistent Deconvolution memberikan hasil yang lebih baik dalam meningkatkan resolusi temporal penampang seismik dibandingkan metode dekonvolusi prediktif. Hasil tersebut diperoleh oleh karena metode Surface Consistent Deconvolution memberikan hasil yang lebih baik dalam memampatkan wavelet, meningkatkan kontinuitas lapisan dan mempertajam reflektor.

Technology and specificity of surface seismic in the Upper Kama Potash Salt Deposit

Exploration surveys at the Upper Kama Potash Salt Deposit widely use the surface seismic method by the common reflection point at depth. Based on the implemented research, a technology is developed for shallow seismic using an explosion source of elastic vibrations for the purposes of geological exploration. The research involved the comparative analysis of the main elastic wave sources used in the shallow seismic. It is highlighted that it is important to consider carefully the near-surface section structure and the surface relief. The accuracy of the velocity analysis procedure in the high-velocity section of salt strata is analyzed. The specificity of acquisition in the shallow seismic with an explosion source is discussed. The actual test data show a considerable increment in the energy of reflections from the roof and floor of the salt strata, which, in the absence of a priori geological information and geophysical logging data (acoustic logging and vertical seismic profiling), affects the velocity analysis precision and, as a consequence, the accuracy of reflection identification at depth. It is found that the explosion source has a much higher signal/noise ratio as against a pulse cartridge, which greatly improves neutrality of interpretation results. The use of a pulse cartridge in the surveys in the depth interval of 200–400 m is only justified when the surface conditions are perfect and the low velocity layer is not thick.

Shallow seismic reflection survey for imaging deep-seated coal layer - Case study from Muara Enim coal

Indonesia has a great potential for deep-seated coal resources. To assist and support the deep-seated coal exploration, a shallow seismic reflection method is applicable for this purpose. This study has conducted a shallow seismic reflection method in Musi Banyuasin Regency, South Sumatera Province. The Muara Enim coal target varies from 100 to 500 meters from the surface. The thickness of the coal layer varies from 2 to 10.65 meters. This study uses 48 channels with 14 Hz single geophone and MiniSosie as the energy source. The receiver and source interval is 15 meters. This study uses a fixed receiver and moving source configuration. From the interpreted seismic section, this study identified a deep-seated coal layer target. These layers are Mangus, Burung, Benuang, Kebon and Benakat layers. A simple interpretation is analyzed by combining the seismic amplitude characteristics and the thickness of the coal layer from the borehole data. From the interpreted seismic section, deep-seated coal layer targets have strong amplitude characteristics and are continuous from southwest to the northeast with a down-dip of around 20-30°. This study helps to inform the operator companies who develop the utilization of deep-seated coal (coalbed methane, underground coal gasification and underground coal mining) about the effective and proper geophysical method for imaging deep-seated coal layer.

Results of studying the azimuthal anisotropy of the Paleozoic basement with VSP technique at the Bystrovka vibroseismic test site

At present due to depletion of reserves in the majority of Western Siberia oil and gas fields, with reservoirs mainly related to lower Cretaceous and Jurassic section interval, the basement intervals present primary scientific and practical interest for prospecting and exploration. At the Bystrovka vibroseismic test site (Novosibirsk region), the Paleozoic basement occurs at depth of about 10 m. This allowed investigating its elastic properties with shallow seismic technique using VSP. Results of these investigations are presented in the present paper.

Joint petrophysical full-waveform inversion of the shallow-seismic and multi-offset GPR data

<p>Shallow-seismic surface wave and ground penetrating radar (GPR) are employed in a wide range of engineering and geosciences applications. Full-waveform inversion (FWI) of either seismic or multi-offset GPR data are able to provide high-resolution subsurface characterization and have received particular attention in the past decade. Those two geophysical methods are involved in the increasing requirements of comprehensive site and material investigations. However, it is still challenging to provide an effective integration between seismic data and electromagnetic data. In this paper, we investigated the joint petrophysical inversion (JPI) of shallow-seismic and multi-offset GPR data for more consistent imaging of near surface. As a bridge between the seismic parameters (P-wave velocity, S-wave velocity, and density) and GPR parameters (relative dielectric permittivity and electric conductivity), the petrophysical relationships with the parameters namely porosity and saturation are employed to link two data sets. We first did a sensitivity analysis of the petrophysical parameters to the seismic and GPR parameters and then determined an efficient integration of using shallow-seismic FWI to update porosity and GPR FWI to update saturation, respectively. A comparison of several parameterisation combinations shows that the seismic velocity parameterisation in shallow-seismic FWI and a modified logarithm parameterisation in GPR FWI works well in reconstructing reliable S-wave velocity and relative dielectric permittivity models, respectively. With the help from the petrophysical links, we realized JPI by transforming those well recovered parameters to the petrophysical parameters and then to other seismic and GPR parameters. A synthetic test indicates that, compared with the individual petrophysical inversion and individual FWI, JPI outperforms in simultaneously reconstructing all seismic, GPR, and petrophysical parameters with higher resolution and improved details. It is proved that JPI would be a potential data integration approach for the shallow subsurface investigation.</p>

Bathymetry and Shallow Seismic Imaging of the 2018 Flank Collapse of Anak Krakatau

The flank failure and collapse of Anak Krakatau on December 22nd, 2018 triggered a destructive tsunami. Whether the prior activity of the volcano led to this collapse, or it was triggered by another means, remains a challenge to understand. This study seeks to investigate the recent volcano submarine mass-landslide deposit and emplacement processes, including the seafloor morphology of the flank collapse and the landslide deposit extent. Bathymetry and sparker seismic data were used during this study. Bathymetry data collected in August, 2019 shows the run-out area and the seafloor landslide deposit morphology. Bathymetry data acquired in May, 2017, is used as the base limit of the collapse to estimate the volume of the flank collapse. Comparisons between seismic data acquired in 2017 and 2019 provide an insight into the landslide emplacement processes, the deposit sequence, and structure below the seafloor. From these results we highlight two areas of the submarine-mass landslide deposit, one proximal to Anak Krakatau island (∼1.6 km) and one distal (∼1.4 km). The resulting analysis suggests that the submarine-mass landslide deposit might be produced by a frontally compressional, faulted, landslide, triggered by the critical stability slope, and due to the recent volcanic activity. Blocky seabed features clearly lie to the southwest of Anak Krakatau, and may represent the collapse blocks of the landslide. The seismic analysis of the data acquired in August, 2019 reveals that the blocky facies extends to ∼1.62 km in the width around Anak Krakatau, and the block thicknesses vary up to 70.4 m. The marine data provides a new insight into the landslide run out and extent, together with the landslide deposit morphology and structure that are not available from satellite imagery or subaerial surveys. We conclude that the landslide run out area southwest of the recent collapse, is ∼7.02 ± 0.21 km2.