Uncertainties of Seismic Source Determination Using a 3-Component Single Station.

Abstract Bukittinggi city area is exposed substantial risk of both, close to seismic source line and site amplification due to soft surface sediment / soil layer. The Great Sumateran Fault (GSF) which is crossing this area, notorious as a very active seismic source. Its responsible to some major earthquake in the vicinity of the fault line. Generally, Bukittinggi area is covered by volcanic product as pumiceous tuff. We applied combined array and single station microtremor measurement to characterize near surface sediment in this area. Based on analysis microtremor single station and array using spatial autocorrelation (SPAC) method, weathered surface layer thickness is in the range of 0-108 m with shear wave velocity in the range of 62-190 m/s, while the fresh pumiceous tuff is in the range of 375-629 m/s. The estimation of site amplification in this area which is indicated by mean amplification is in the range of 1-1.95. The high amplification zone is occupies the northernmost area and some area locally in the southern part of Bukittinggi city.

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Advances in 6C seismology: Applications of combined translational and rotational motion measurements in global and exploration seismology

Geophysics ◽

10.1190/geo2017-0492.1 ◽

2018 ◽

Vol 83 (3) ◽

pp. WC53-WC69 ◽

Cited By ~ 17

Author(s):

Cedric Schmelzbach ◽

Stefanie Donner ◽

Heiner Igel ◽

David Sollberger ◽

Taufiq Taufiqurrahman ◽

...

Keyword(s):

Rotational Motion ◽

Tomographic Reconstruction ◽

High Sensitivity ◽

Seismic Source ◽

Motion Sensors ◽

S Wave ◽

Single Station ◽

Potential Applications ◽

Global Seismology ◽

Motion Measurements

Over the past few decades, the potential of collocated measurements of 6C data (3C of translational and 3C of rotational motion) has been demonstrated in global seismology using high-sensitivity, observatory-based ring laser technology. Proposed applications of 6C seismology range from tomographic reconstruction of near-receiver structure to the reduction of nonuniqueness in seismic source inverse problems. Applications to exploration problems have so far been hampered by the lack of appropriate sensors, but several applications have been proposed and demonstrated with array-derived rotational motion estimates. With the recent availability of, for example, fiber-optic-based high-sensitivity rotational motion sensors, widespread applications of 6C techniques to exploration problems are in sight. Potential applications are based on, for example, the fact that the extended set of combined translational and rotational motion observations enables carrying out array-type processing with single-station recordings such as wavefield separation and surface-wave suppression. Furthermore, measuring the rotational component (curl) of the seismic wavefield enables direct isolation of the S-wave constituents and could significantly improve S-wave exploration. Rotational measurements provide estimates of the spatial wavefield gradient at the free surface that allow carrying out analyses such as local slowness estimation and wavefield reconstruction. Furthermore, rotational motion measurements can help to resolve wavefield infidelity introduced by seismic instruments that are not well-coupled to the ground.

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F-K analysis of NORESS array and single station data to identify sources of near-receiver and near-source scattering

Bulletin of the Seismological Society of America ◽

10.1785/bssa08006b2227 ◽

1990 ◽

Vol 80 (6B) ◽

pp. 2227-2241

Author(s):

I. N. Gupta ◽

C. S. Lynnes ◽

T. W. McElfresh ◽

R. A. Wagner

Keyword(s):

Arrival Time ◽

Secondary Phase ◽

Seismic Source ◽

Polarization Characteristic ◽

P Waves ◽

Earthquake Sources ◽

Power Difference ◽

Short Period ◽

Single Station ◽

Basin Boundaries

Abstract F-k analyses of short-period recordings of both explosion and earthquake sources at the high-frequency NORESS array indicate secondary arrivals from a near-receiver source about 25 to 30 km southwest of the array. Use of residual seismograms, derived by subtracting the beamed record from each array channel, improved the identification of the same scatterer. F-k power difference plots, obtained by subtracting (after normalization) the f-k power versus slowness estimates for the initial P window from those for the latter windows, provided nearly identical results. The secondary seismic source appears to be short-period surface waves, Rg, generated by the scattering of incident P waves in the region of Lake Mjosa, 27 km southwest of NORESS, where there is about 1 km of relief from the bottom of the lake to the top of an adjacent hill. Polarization analysis of an explosion recorded on three-component elements of NORESS also suggested a secondary phase with polarization characteristic of Rg and arrival time and azimuth consistent with those derived from the f-k analysis. Near-source scattering is investigated by f-k analysis of data from reciprocal arrays formed by interchanging the roles of source and receiver. Application to closely spaced Yucca Flat (NTS) shots recorded at several stations provides evidence for Rg → P scattering near the northwestern and other basin boundaries of the Yucca Valley. It seems that deterministic locations of near-receiver P → Rg and near-source Rg → P scattering can be obtained by f-k techniques.

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The assessment of local site effects and dynamic behaviour in Nicosia, Cyprus

Geofizika ◽

10.15233/gfz.2021.38.1 ◽

2021 ◽

Vol 38 (1) ◽

pp. 61-80

Author(s):

Hilmi Dindar ◽

Mustafa Akgün ◽

Cavit Atalar ◽

Özkan Cevdet Özdağ

Keyword(s):

Seismic Waves ◽

Eastern Mediterranean ◽

Seismic Source ◽

Vulnerability Index ◽

Peak Period ◽

Single Station ◽

Lithospheric Plates ◽

Masw Method ◽

Earthquake Zone ◽

Soil Behaviour

Single-station microtremor measurements were conducted to investigate earthquake and soil behaviour for the first time in Nicosia, Cyprus. Cyprus is located in a tectonically complex area in the Eastern Mediterranean where three plates meet. The study area was chosen to cover the areas to be opened for new development. Nicosia, the capital of Cyprus, is also the island's most important cultural, industrial, commercial, and transportation centre. The study creates base maps for the soil to assess earthquake resistance crucial for construction. Microtremor Method was applied at 100 stations and the Multi-Channel Analysis of Surface Waves (MASW) method was used at 52 stations. Also, RefractionMicrotremor (Re-Mi) and L-Shaped Spatial Autocorrelation (L-SPAC) methods were carried out at 17 stations to substantiate the research. The results of the microtremor method indicate that the predominant soil period values have an average of 1 second and pre-dominant peak period values are generally found between 0.1 to 5 s at the study area. Peak amplitude values are observed between 1 and 2.4. The Vulnerability Index Parameter (Kg) exceeded 20 at the central and the southern stations, and Kg values change between 7 and 54 units. The Kg values were found to be higher than 20 in soils where shear wave velocity is lower than 760 m/s. At the same time, the values of the predominant peak period were greater than 1 second. Cyprus is located in the Alpine Himalayan earthquake zone. The Cyprus Arc is known as the main seismic source of the island, It constitutes the tectonic border among African and Eurasian lithospheric plates in the region. During an earthquake in Nicosia, seismic waves will be amplified by an average of 1.5 times and soil deformation will occur due to the exceeding elastic limits. The results provided important insight into soil behaviour and indicated its reactions in a potential earthquake.

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