scholarly journals Ice Thickness Estimation from Geophysical Investigations on the Terminal Lobes of Belvedere Glacier (NW Italian Alps)

2019 ◽  
Vol 11 (7) ◽  
pp. 805 ◽  
Author(s):  
Chiara Colombero ◽  
Cesare Comina ◽  
Emanuele De Toma ◽  
Diego Franco ◽  
Alberto Godio
Keyword(s):  
Spectral Ratio ◽  
Working Environment ◽  
Ice Thickness ◽  
Italian Alps ◽  
Thickness Estimation ◽  
Reference Base ◽  
Single Station ◽  
Passive Seismic ◽  
Geophysical Investigations ◽  
Seismic Measurements

: Alpine glaciers are key components of local and regional hydrogeological cycles and real-time indicators of climate change. Volume variations are primary targets of investigation for the understanding of ongoing modifications and the forecast of possible future scenarios. These fluctuations can be traced from time-lapse monitoring of the glacier topography. A detailed reconstruction of the ice bottom morphology is however needed to provide total volume and reliable mass balance estimations. Non-destructive geophysical techniques can support these investigations. With the aim of characterizing ice bottom depth, ground-penetrating radar (GPR) profiles and single-station passive seismic measurements were acquired on the terminal lobes of Belvedere Glacier (NW Italian Alps). The glacier is covered by blocks and debris and its rough topography is rapidly evolving in last years, with opening and relocation of crevasses and diffuse instabilities in the frontal sectors. Despite the challenging working environment, ground-based GPR surveys were performed in the period 2016–2018, using 70-MHz and 40-MHz antennas. The 3D ice bottom morphology was reconstructed for both frontal lobes and a detailed ice thickness map was obtained. GPR results also suggested some information on ice bottom properties. The glacier was found to probably lay on a thick sequence (more than 40 m) of subglacial deposits, rather than on stiff bedrock. Week deeper reflectors were identified only in the frontal portion of the northern lobe. These interfaces may indicate the bedrock presence at a depth of around 80 m from the topographic surface, rapidly deepening upstream. Single-station passive seismic measurements, processed with the horizontal-to-vertical spectral ratio (HVSR) method, pointed out the absence of sharp vertical contrast in acoustic impedance between ice and bottom materials, globally confirming the hypotheses made on GPR results. The obtained results have been compared with previous independent geophysical investigations, performed in 1961 and 1985, with the same aim of ice thickness estimation. The comparison allowed us to validate the results obtained in the different surveys, supply a reference base map for the glacier bottom morphology and potentially study ice thickness variations over time.

scholarly journals Antarctic ice sheet thickness estimation using the horizontal-to-vertical spectral ratio method with single-station seismic ambient noise

2018 ◽  
Vol 12 (2) ◽  
pp. 795-810 ◽  
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Spectral Ratio ◽  
Ice Thickness ◽  
Antarctic Ice Sheet ◽  
Seismic Stations ◽  
Thickness Estimation ◽  
Seismic Ambient Noise ◽  
The Antarctic

Abstract. We report on a successful application of the horizontal-to-vertical spectral ratio (H / V) method, generally used to investigate the subsurface velocity structures of the shallow crust, to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness measured at each station has comparable accuracy to the Bedmap2 database. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H / V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thicknesses were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H / V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single- and two-layer ice sheets, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were in good concurrence with the Bedmap2 ice thickness database, and that ice thickness differences between the two were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to two hours for reliable ice sheet thickness estimation using the H / V method. This study extends the application fields of the H / V method and provides an effective and independent way to measure ice sheet thickness in Antarctica.

scholarly journals Antarctic ice-sheet structures retrieved from P-wave coda autocorrelation method and comparisons with two other single-station passive seismic methods

2019 ◽  
Vol 66 (255) ◽  
pp. 153-165
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao
Keyword(s):  
Ice Sheet ◽  
Spectral Ratio ◽  
Receiver Functions ◽  
P Wave ◽  
Polar Regions ◽  
Seismic Methods ◽  
Single Station ◽  
Passive Seismic ◽  
Glacier Ice ◽  
Autocorrelation Method

AbstractPassive seismology is becoming increasingly popular for glacier/ice-sheet structure investigations in Polar regions. Single-station passive seismic methods including P-wave receiver functions (PRFs), horizontal-to-vertical spectral ratio (HVSR) and a recently proposed autocorrelation method have been used to retrieve glacier/ice-sheet structures. Despite their successful applications, analysis regarding their detection abilities in different glaciological environments has not been reported. In this study, we compare ice thicknesses and vp/vs ratios obtained from the three methods using data collected at GAMSEIS and POLENET/ANET seismic arrays in Antarctica. Ice thickness estimates derived from the three methods are found to be consistent. Comparisons conducted under various model setups, including those involving tiled layers and sedimentary layers, show that the effectiveness of the autocorrelation method is not superior to the PRF method for retrieving ice-sheet structures. The autocorrelation method however can complement other methods as it only requires a single component seismic record.

scholarly journals Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station seismic ambient noise

2017 ◽  
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Spectral Ratio ◽  
Ice Thickness ◽  
Antarctic Ice Sheet ◽  
Seismic Stations ◽  
Thickness Estimation ◽  
Seismic Ambient Noise ◽  
The Antarctic

Abstract. The horizontal-to-vertical spectral ratio (H/V) method implemented at single stations using seismic ambient noise waveforms is a fast, noninvasive, efficient method to investigate the subsurface velocity structures of the shallow crust. In this study, we report on a successful application of the H/V method to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness at each station was reliably measured. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H/V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thickness were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H/V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single and two-layer ice sheet, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were highly consistent with the Bedmap2 ice thickness database, and their ice thickness differences were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to 1–2 hours for reliable ice sheet thickness estimation using the H/V method. This study extends the application fields of the H/V method and provides a complementary and independent way to measure ice sheet thickness in Antarctica.

scholarly journals The Soft Layer Thickness Estimation using Microtremor Measurement to Identify Landside Potential in Watukumpul, Central Java, Indonesia.

2021 ◽  
Vol 6 (1) ◽  
pp. 16-23
Author(s):  
Urip Nurwijayanto Prabowo ◽  
Akmal Ferdiyan ◽  
Ayu Fitri Amalia
Keyword(s):  
Layer Thickness ◽  
Spectral Ratio ◽  
Dominant Frequency ◽  
Soil Slope ◽  
Soft Layer ◽  
Thickness Estimation ◽  
Central Java ◽  
Hvsr Method ◽  
Microtremor Measurement ◽  
Potential Area

Watukumpul is an area that is prone to landslides, so determining the soft layer thickness is very important to identify the landslide potential. The soft layer thickness can be estimated using microtremor signal measurements which analyzed using the Horizontal to Vertical Spectral Ratio (HVSR). In this study,we measured microtremor signal of 33location around Watukumpul, Pemalang, Central Java area to determine soft layer thickness. Micretremor signal was analyzed based on theHVSR method using Geopsy software and follow the standard of the Sesame Europan Project. The results of the HVSR method are the HVSR curve that fulfills the reliable curve standard. HVSR curve shows that the dominant frequency of soft layer ranges from 1.36 – 7.62 Hz and the amplification values ranges from 9.00 – 41.45. The soft layer thickness value in the study area ranges from 17.58 - 103.60 meters. The high landslide potential area are located at W7, W8, W18, W30 and W32 where has thin soft layer and high soil slope.

scholarly journals Ice Thickness and Sea Depth Derived from Reflection-Seismic Measurements on the Central Part of Filchner-Ronne Ice Shelf, Antarctica

1988 ◽  
Vol 11 ◽  
pp. 14-18 ◽  
Author(s):  
J. Determann ◽  
F. Thyssen ◽  
H. Engelhardt
Keyword(s):  
Drill Hole ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Reflection Seismic ◽  
Seismic Records ◽  
3D Processing ◽  
Seismic Measurements ◽  
Good Agreement ◽  
Made In

In January 1986, reflection-seismic measurements were made in the central part of Filchner-Ronne Ice Shelf, north of Henry and Korff ice rises, by a German oversnow traverse. With the help of a newly developed “ice streamer”, two people were able to obtain seismic records nearly every 5km over a distance of 150km within 3d. Processing of digitally recorded seismograms yielded profiles of ice thickness and sea depth. The ice thickness varies from 400 to 500 m and is in good agreement with the thickness of 465 m at a drill hole. The reflection-seismic results are comparable with those obtained from aerogeophysical measurements.

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