GPS Height and Gravity Variations Due to Ocean Tidal Loading Around Taiwan

Yeh, Teng Kuang; Huang, Cheinway; Xu, Guochang

doi:10.1007/s10712-008-9041-3

Cited by 12 publications

(4 citation statements)

References 20 publications

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“…Meanwhile, an average rate close to 6.17 × 10 −6 m/s derived from the associated oscillation of the Earth's surface also shows an agreement with the seismic data. Note that the frequency of the amplification is different compared with the well-known frequency-dependent effects (such as the lunar elliptic tides, lunar semi-diurnal tides, lunar-solar semi-diurnal tides and so on) on the surface displacements [25,26].…”

Section: Introductionmentioning

confidence: 98%

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Chen

Yeh

et al. 2020

Remote Sensing

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Broadband seismometers, ground-based Global Navigation Satellite Systems (GNSS), and magnetometers that were located within an epicentral distance of approximately 150 km consistently observed the novel anomalous behaviors of the common-mode ground vibrations approximately 5–10 days before the M6.6 Meinong earthquake in Taiwan. The common-mode ground vibrations with amplitudes near 0.1 m at frequencies ranging from 8 × 10−5 to 2 × 10−4 Hz were generated near the region close to the epicenter of the impending earthquake. The common-mode vibrations were consistently observed in seismic and GNSS data associated with five other earthquakes in four distinct areas. The results reveal that the common-mode vibrations could be a typical behavior before earthquakes. The causal mechanism of common-mode vibrations can be attributed to crustal resonance excitations before fault dislocations occur. Potential relationships with other pre-earthquake anomalies suggest that the common-mode vibrations could be ground motion before earthquakes, which was investigated for a significant length of time.

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Section: Introductionmentioning

confidence: 98%

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Chen

Yeh

et al. 2020

Remote Sensing

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“…This was shown in a study of OTL corrections for superconducting gravity (SG) measurements at the Hsinchu station by Hwang et al (2009), who found that some of the global OTL programs produce anomalously large values that cannot be used for gravity corrections. The Hsinchu SG station is about 8.6 km to the Taiwan Strait and situated at an elevation of 78 m. Earlier studies suggest that gravity effects and displacements due to OTL can be very large at offshore islands with large tidal amplitudes (Lambert et al 1998;Yamamoto et al 2001;Huang et al 2008;Yeh et al 2008;Hwang et al 2009). …”

Section: Introductionmentioning

confidence: 99%

SGOTL: A Computer Program for Modeling High-Resolution, Height-Dependent Gravity Effect of Ocean Tide Loading

Hwang¹,

Huang²

2012

Terr. Atmos. Ocean. Sci.

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SGOTL, a computer package coded in FORTRAN, has been developed to model the gravity effect due to ocean tide loading (OTL), especially for a coastal station with large ocean tides. SGOTL uses a regional and a global tide model to account separately for near (inner) and far (outer) zone contributions, and optimizes an inner-zone region and grid interval for numerical convolution. Height dependent Green's functions for Newtonian and elastic effects are developed. The coastline is defined by the full-resolution GMT shoreline, and optionally a digital elevation model (DEM). A case study using gravity observations at the Hsinchu superconducting gravity station and some offshore islands around the Taiwan Strait suggests that SGOTL outperforms some selected global OTL programs and achieves an accuracy of 0.1 μGal for 8 leading tidal constituents.

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“…Regarding short-term variations, offsets in GPS coordinate time-series data before and after earthquakes are frequently presented to illustrate co-seismic dislocations [2,[13][14][15]. In addition, GPS signals also carry obvious annual and semiannual cycles along with tropospheric delay, ionospheric refraction, and ocean tidal loading [16][17][18][19]. These aforementioned effects need to first be removed from and/or mitigated in GPS data in order to effectively retrieve surface displacements in earthquake preparation periods.…”

Section: Introductionmentioning

confidence: 99%

Unique Pre-Earthquake Deformation Patterns in the Spatial Domains from GPS in Taiwan

et al. 2020

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Most earthquakes are considered to be caused by stress accumulating in and subsequently releasing from the crust. To extract non-linear and non-stationary earthquake-induced signals associated with stress accumulation, the Hilbert–Huang transform was utilized to filter long-term movements, short-term noise, and frequency-dependent (annual and semi-annual) variations from surface displacements measured by the global positioning system (GPS) in Taiwan. Earthquake-related surface displacements were expressed as horizontal directions (i.e., GPS azimuths) using the north–south and east–west components of residual GPS data to bypass influences resulted from the inhomogeneous nature of the crust. Analytical results showed that the relationships between earthquake occurrence and the aligned GPS azimuth passed the statistical test of the Molchan’s error diagram. Aligned GPS azimuths were in agreement with direction of earthquake-related P axes for 81% (26/32) studied events. Areas with the highest paralleling orientations of GPS azimuths appeared around epicenters several days to weeks before earthquake occurrence. Durations from aligned GPS azimuths to earthquake occurrence are roughly proportional to earthquake magnitude. Similar variations of the GPS azimuths were observed in GPS data containing or excluding co-seismic dislocation (i.e., one day before) in the temporal and spatial domain. These suggest that the aligned GPS azimuth could be a promising anomalous phenomenon for studying crustal deformation before earthquakes.

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GPS Height and Gravity Variations Due to Ocean Tidal Loading Around Taiwan

Cited by 12 publications

References 20 publications

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

SGOTL: A Computer Program for Modeling High-Resolution, Height-Dependent Gravity Effect of Ocean Tide Loading

Unique Pre-Earthquake Deformation Patterns in the Spatial Domains from GPS in Taiwan

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