scholarly journals Imaging and Monitoring Temporal Changes of Shallow Seismic Velocities at the Garner Valley Near Anza, California, Following the M7.2 2010 El Mayor‐Cucapah Earthquake

2020 ◽  
Vol 125 (1) ◽  
Author(s):  
Lei Qin ◽  
Yehuda Ben‐Zion ◽  
Luis Fabian Bonilla ◽  
Jamison H. Steidl
Keyword(s):  
Temporal Changes ◽  
Seismic Velocities ◽  
Shallow Seismic

Upper Mississippi embayment shallow seismic velocities measured in situ

1997 ◽  
Vol 46 (3-4) ◽  
pp. 313-330 ◽  
Author(s):  
Hsi-Ping Liu ◽  
Yiguang Hu ◽  
James Dorman ◽  
Tzyy-Shiou Chang ◽  
Jer-Ming Chiu
Keyword(s):  
Seismic Velocities ◽  
Mississippi Embayment ◽  
Shallow Seismic ◽  
Upper Mississippi Embayment

A vertical array method for shallow seismic refraction surveying of the sea floor

Geophysics ◽  
1990 ◽  
Vol 55 (1) ◽  
pp. 92-96 ◽  
Author(s):  
J. A. Hunter ◽  
S. E. Pullan
Keyword(s):  
Seismic Refraction ◽  
Research Interest ◽  
Seismic Velocities ◽  
Vertical Array ◽  
Sea Floor ◽  
Site Investigations ◽  
Shallow Seismic ◽  
Continental Shelves ◽  
Defense Research ◽  
Research Studies

In recent years, specific requirements of offshore geotechnical site investigations, as well as detailed defense research studies, have stimulated research interest in methods for measuring seismic velocities of sea‐floor sediments on the continental shelves. Investigations have used wide‐angie subbottom reflection measurements (McKay and McKay, 1982), bottom‐laid refraction cables (Hunter et al., 1979), and towed refraction arrays, both on the surface (Hunter and Hobson, 1974) and at depth (Fortin et al., 1987; Fagot, 1983).

Imaging and monitoring of the shallow subsurface using spatially windowed surface-wave analysis with a single permanent seismic source

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. EN23-EN38 ◽  
Author(s):  
Tatsunori Ikeda ◽  
Takeshi Tsuji ◽  
Masashi Nakatsukasa ◽  
Hideaki Ban ◽  
Ayato Kato ◽  
...  
Keyword(s):  
Surface Wave ◽  
Temporal Stability ◽  
Spatial Variations ◽  
Storage Site ◽  
Seismic Velocities ◽  
Wave Analysis ◽  
Spatiotemporal Resolution ◽  
Shallow Subsurface ◽  
Phase Velocities ◽  
Shallow Seismic

Development of shallow subsurface monitoring systems is important for monitoring the ground stability of shallow formation, and also for conventional deep seismic monitoring because with current techniques, temporal changes in shallow seismic velocities can influence monitoring results for the deep subsurface. We have developed an effective shallow seismic imaging and monitoring system with high spatiotemporal resolution and accuracy using a continuous and controlled source system, the accurately controlled routinely operated signal system (ACROSS). The method applies surface-wave analysis to characterize and monitor the shallow subsurface from the spatiotemporal variation of phase velocities. Because the number of available ACROSS units is usually limited, estimating a shallow subsurface with high spatial resolution is a challenging issue in ACROSS-based monitoring. To overcome this problem, we introduced a 2D spatial window into multichannel analysis of surface waves. We analyzed continuous ACROSS data acquired during seven different data periods from 2014 to 2016 at the Aquistore [Formula: see text] storage site in Canada. As a result, we clearly estimated spatial variations of phase velocities using only a single ACROSS unit. The numerical experiments of our method suggested that the spatial variations could be associated with shallow geologic boundaries in the study area. We identified clear seasonal variations of phase velocities in winter, possibly related to ground freezing in shallow sediments, and we showed the high temporal stability of our monitoring approach in warmer seasons. These results indicated that our approach would have the potential to identify spatiotemporal change in shallow subsurface associated with natural phenomena or fluid leakage.

Regional seismic velocity changes following the 2019 Mw7.1 Ridgecrest California earthquake from autocorrelations and P/S converted waves

2021 ◽  
Author(s):  
Y Lu ◽  
Y Ben-Zion
Keyword(s):  
Temporal Resolution ◽  
Seismic Velocity ◽  
Time Windows ◽  
Regional Scale ◽  
Early Period ◽  
Temporal Changes ◽  
High Temporal Resolution ◽  
Seismic Velocities ◽  
Seismic Velocity Changes ◽  
Velocity Changes

Summary We examine regional transient changes of seismic velocities generated by the Mw 7.1 2019 Ridgecrest earthquake in California, using autocorrelations of moving time windows in continuous waveforms recorded at regional stations. We focus on travel time differences in a prominent phase generated by an interface around 2 km depth, associated with transmitted Pp waves and converted Ps waves from the ongoing microseismicity. Synthetic tests demonstrate the feasibility of the method for monitoring seismic velocity changes. Taking advantage of the numerous aftershocks in the early period following the mainshock, we obtain a temporal resolution of velocity changes up to 20 min in the early post-mainshock period. The results reveal regional coseismic velocity drops in the top 1–3 km with an average value of ∼2 per cent over distances up to 100 km from the Ridgecrest event. These average velocity drops are likely dominated by larger changes in the shallow materials, and are followed by rapid recoveries on timescales of days. Around the north end of the Ridgecrest rupture and the nearby Coso geothermal region, the observed coseismic velocity drops are up to ∼8 per cent. The method allows monitoring temporal changes of seismic velocities with high temporal resolution, fast computation, and precise spatial mapping of changes. The results suggest that significant temporal changes of seismic velocities of shallow materials are commonly generated on a regional scale by large events.

scholarly journals Temporal changes of seismic velocities in the San Jacinto Fault zone associated with the 2016 Mw 5.2 Borrego Springs earthquake

2019 ◽  
Vol 220 (3) ◽  
pp. 1536-1554 ◽  
Author(s):  
Hongrui Qiu ◽  
Gregor Hillers ◽  
Yehuda Ben-Zion
Keyword(s):  
Fault Zone ◽  
Temporal Changes ◽  
Coda Wave ◽  
Seismic Velocities ◽  
Rupture Directivity ◽  
Lapse Time ◽  
Near Surface ◽  
Fault Surface ◽  
San Jacinto Fault ◽  
San Jacinto Fault Zone

SUMMARY We study temporal changes of seismic velocities associated with the 10 June 2016 Mw 5.2 Borrego Springs earthquake in the San Jacinto fault zone, using nine component Green's function estimates reconstructed from daily cross correlations of ambient noise. The analysed data are recorded by stations in two dense linear arrays, at Dry Wash (DW) and Jackass Flat (JF), crossing the fault surface trace ∼3 km northwest and southeast of the event epicentre. The two arrays have 9 and 12 stations each with instrument spacing of 25–100 m. Relative velocity changes (δv/v) are estimated from arrival time changes in the daily correlation coda waveforms compared to a reference stack. The obtained array-average δv/v time-series exhibit changes associated with the Borrego Springs event, superposed with seasonal variations. The earthquake-related changes are characterized by a rapid coseismic velocity drop followed by a gradual recovery. This is consistently observed at both arrays using time- and frequency-domain δv/v analyses with data from different components in various frequency bands. Larger changes at lower frequencies imply that the variations are not limited to the near surface material. A decreasing coseismic velocity reduction with coda wave lapse time indicates larger coseismic structural perturbations in the fault zone and near-fault environment compared to the surrounding rock. Observed larger changes at the DW array compared to the JF array possibly reflect the northwestward rupture directivity of the Borrego Springs earthquake.

scholarly journals Temporal seismic wave velocity variations at Láscar volcano

2016 ◽  
Vol 43 (2) ◽  
pp. 240 ◽  
Author(s):  
Diego M. González ◽  
Klaus Bataille ◽  
Tom Eulenfeld ◽  
Luis E. Franco
Keyword(s):  
Seismic Wave ◽  
Complex Structure ◽  
Temporal Changes ◽  
Velocity Variation ◽  
Dynamic Processes ◽  
Seismic Events ◽  
Seismic Velocities ◽  
Seismic Wave Velocity ◽  
The Earth ◽  
Lascar Volcano

We report on the first study using Seismic Wave Interferometry to determine variations of seismic velocities through time, in the vicinity of Láscar volcano in Chile. Seismic Wave Interferometry has been used as a powerful tool to determine spatial and temporal changes of seismic velocities within the Earth. Spatial variations of seismic velocities are related to heterogeneities of material properties, which are expected to occur in a complex structure. However, temporal changes are indicative of dynamic process within the elastic media, and thus, this tool can be used to monitor dynamic processes at volcanic zones. We find consistent variations on three stations close to the volcano, with dv/v of ±0.6%, most likely related to the inflation/deflation process due to fluid movement of magmatic or hydrothermal origin within the volcanic structure. During the observed period of velocity variation, OVDAS reported an increase of volcanic activity evidenced by the increase of the number of long period seismic events, increase of gas emissions and the formation of incandescence above the crater. We suggest that this tool can contribute to the understanding of volcano related dynamic processes, as well as for routine volcano monitoring purposes.

Sign in / Sign up

Export Citation Format

Share Document