Current Activity of the Long Point Fault in Houston, Texas Constrained by Continuous GPS Measurements (2013–2018)

The Long Point Fault is one of the most active urban faults in Houston, Texas, which belong to a complex system of normal growth faults along the Texas Gulf Coast. To assess the activity of the Long Point Fault, a GPS array with 12 permanent stations was installed along the two sides of the 16-km-long fault scarp in 2013. GPS datasets were processed with the Precise Point Positioning (PPP) and Double-Difference (DD) methods. The daily PPP solutions with respect to the International Global Navigation Satellite System (GNSS) Reference Frame 2014 (IGS14) were converted to the Stable Houston Reference Frame (Houston16). The six-year continuous GPS observations indicate that the Long Point Fault is currently inactive, with the rates of down-dip-slip and along-strike-slip being below 1 mm/year. The Long Point Fault area is experiencing moderate subsidence varying from 5 to 11 mm/year and a coherent horizontal movement towards the northwest at a rate of approximately 2 to 4 mm/year. The horizontal movement is induced by the subsidence bowl that has been developing since the 1980s in the Jersey Village area. Current surficial damages in the Long Point Fault area are more likely caused by ongoing uneven subsidence and its induced horizontal strains, as well as the significant seasonal ground deformation, rather than deep-seated or tectonic-controlled fault movements. The results from this study suggest a cause-and-effect relationship between groundwater withdrawals and local faulting, which is pertinent to plans for future urban development, use of groundwater resources, and minimization of urban geological hazards.

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GPS geodetic infrastructure for subsidence and fault monitoring in Houston, Texas, USA

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-382-11-2020 ◽

2020 ◽

Vol 382 ◽

pp. 11-18 ◽

Cited By ~ 1

Author(s):

Gonzalo Agudelo ◽

Guoquan Wang ◽

Yuhao Liu ◽

Yan Bao ◽

Michael J. Turco

Keyword(s):

Reference Frame ◽

Urban Areas ◽

Ground Deformation ◽

University Of Houston ◽

Fault Monitoring ◽

Global Positioning ◽

The Stability ◽

Continuous Gps ◽

The University ◽

Regional Reference

Abstract. Houston, Texas, is one of the earliest urban areas to employ Global Positioning System (GPS) technology for land subsidence and fault monitoring. As of 2020, the University of Houston and the Harris-Galveston Subsidence District have integrated over 230 permanent GPS stations into their routine GPS data processing for regional subsidence and fault monitoring. This article summarizes the GPS geodetic infrastructure in the Greater Houston region. The infrastructure is comprised of two components: a dense GPS network (HoustonNet) and a stable regional reference frame (Houston20). Houston20 is realized by 25 long-history (>8 years) continuous GPS stations located outside the subsiding area and is aligned in origin and scale with the International GNSS Reference Frame 2014 (IGS14). The stability of the regional reference frame is below 1 mm yr−1 in all three directions. GPS-derived ground deformation rates (2010–2019) within the Greater Houston region are also presented in this article.

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A Single-Difference Multipath Hemispherical Map for Multipath Mitigation in BDS-2/BDS-3 Short Baseline Positioning

Remote Sensing ◽

10.3390/rs13020304 ◽

2021 ◽

Vol 13 (2) ◽

pp. 304

Author(s):

Chao Liu ◽

Yuan Tao ◽

Haiqiang Xin ◽

Xingwang Zhao ◽

Chunyang Liu ◽

...

Keyword(s):

Satellite System ◽

Observation Time ◽

Double Difference ◽

Observation Data ◽

Multipath Mitigation ◽

Short Baseline ◽

Independent Variables ◽

Positioning Errors ◽

Single Difference ◽

Repeat Time

The BeiDou Navigation Satellite System (BDS) features a heterogeneous constellation so that it is difficult to mitigate the multipath in the coordinate-domain. Therefore, mitigating the multipath in the observation-domain becomes more important. Sidereal filtering is commonly used for multipath mitigation, which needs to calculate the orbit repeat time of each satellite. However, that poses a computational challenge and damages the integrity at the end of the multipath model. Therefore, this paper proposes a single-difference model based on the multipath hemispherical map (SD-MHM) to mitigate the BDS-2/BDS-3 multipath in a short baseline. The proposed method is converted from double-difference residuals to single-difference residuals, which is not restricted by the pivot satellite transformation. Moreover, it takes the elevation and the azimuth angles of the satellite as the independent variables of the multipath model. The SD-MHM overcomes the unequal observation time of some satellites and does not require specific hardware. The experimental results show that the SD-MHM reduces the root mean square of the positioning errors by 56.4%, 63.9%, and 67.4% in the east, north, and vertical directions; moreover, it contributes to an increase in the baseline accuracy from 1.97 to 0.84 mm. The proposed SD-MHM has significant advantages in multipath mitigation compared with the advanced sidereal filtering method. Besides, the SD-MHM also features an excellent multipath correction capability for observation data with a period of more than seven days. Therefore, the SD-MHM provides a universal strategy for BDS multipath mitigation.

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Slip Distribution of the 2020 Mw6.9 Samos Earthquake Using a Bayesian Approach

10.5194/egusphere-egu21-14970 ◽

2021 ◽

Author(s):

Figen Eskikoy ◽

Semih Ergintav ◽

Uğur Dogan ◽

Seda Özarpacı ◽

Alpay Özdemir ◽

...

Keyword(s):

Surface Deformation ◽

Fault Plane ◽

Source Parameters ◽

Geodetic Data ◽

Slip Distribution ◽

Double Difference ◽

Gps Data ◽

Analysis Tool ◽

Finite Fault ◽

Continuous Gps

On 2020 October 30, an Mw6.9 earthquake struck offshore&#160;Samos Island. Severe structural damages were observed in Greek Islands and city of Izmir (Turkey). 114 people lost their lives and more than a thousand people were injured in Turkey. The earthquake triggered local tsunami. Significant seismic activity occurred in this region following the earthquake and ~1800 aftershocks (M>1) were recorded by KOERI within the first three days. In this study, we analyze the slip distribution and aftershocks of the 2020 earthquake.For the aftershock relocations, the continuous waveforms were collected from NOA, Disaster and Emergency Management Authority of Turkey (AFAD) and KOERI networks. The database &#160;&#160;was created based on merged catalogs from AFAD and KOERI. For estimating optimized aftershock location distribution, the P and S phases of the aftershocks are picked manually and relocated with double difference algorithm. In addition, source mechanisms of aftershocks M>4 are obtained from regional body and surface waveforms.The surface deformation of the earthquake was obtained from both descending and ascending orbits of the Sentinel-1 A/B and ALOS2 satellites. Since the rupture zone is beneath the Gulf of Kusadas&#305;, earthquake related deformation in the interferograms can only be observed on the northern part of the Samos Island. We processed all possible pairs chose the image pairs with the lowest noise level.In this study, we used 25 continuous GPS stations which are compiled from TUSAGA-Aktif in Turkey and NOANET in Greece. In addition to continuous GPS data, on 2020 November 1, GPS survey was initiated and the earthquake deformation was measured on 10 GNSS campaign sites (TUTGA), along onshore of Turkey.The aim of this study is to estimate the spatial and temporal rupture evolution of the earthquake from geodetic data jointly with near field displacement waveforms. To do so, we use the Bayesian Earthquake Analysis Tool (BEAT).As a first step of the study, rectangular source parameters were estimated by using GPS data. In order to estimate the slip distribution, we used both ascending and descending tracks of Sentinel-1 data, ALOS2 and GPS displacements. In our preliminary geodetic data based finite fault model, we used the results of focal mechanism and GPS data inversion solutions for the initial fault plane parameters. The slip distribution results indicate that earthquake rupture is ~35 km long and the maximum slip is ~2 m normal slip along a north dipping fault plane. This EW trending, ~45&#176; north dipping normal faulting system consistent with this tectonic regime in the region. This seismically active area is part of a N-S extensional regime and controlled primarily by normal fault systems.AcknowledgementsThis work is supported by the Turkish Directorate of Strategy and Budget under the TAM Project number&#160;2007K12-873.

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Investigation of correlation of the variations in land subsidence (detected by continuous GPS measurements) and methodological data in the surrounding areas of Lake Urmia

Nonlinear Processes in Geophysics ◽

10.5194/npg-19-675-2012 ◽

2012 ◽

Vol 19 (6) ◽

pp. 675-683 ◽

Cited By ~ 5

Author(s):

K. Moghtased-Azar ◽

A. Mirzaei ◽

H. R. Nankali ◽

F. Tavakoli

Keyword(s):

Time Series ◽

Land Subsidence ◽

Salt Lake ◽

Linear Trend ◽

Groundwater Resources ◽

Time Interval ◽

Gps Measurements ◽

Lake Urmia ◽

North West ◽

Continuous Gps

Abstract. Lake Urmia, a salt lake in the north-west of Iran, plays a valuable role in the environment, wildlife and economy of Iran and the region, but now faces great challenges for survival. The Lake is in immediate and great danger and is rapidly going to become barren desert. As a result, the increasing demands upon groundwater resources due to expanding metropolitan and agricultural areas are a serious challenge in the surrounding regions of Lake Urmia. The continuous GPS measurements around the lake illustrate significant subsidence rate between 2005 and 2009. The objective of this study was to detect and specify the non-linear correlation of land subsidence and temperature activities in the region from 2005 to 2009. For this purpose, the cross wavelet transform (XWT) was carried out between the two types of time series, namely vertical components of GPS measurements and daily temperature time series. The significant common patterns are illustrated in the high period bands from 180–218 days band (~6–7 months) from September 2007 to February 2009. Consequently, the satellite altimetry data confirmed that the maximum rate of linear trend of water variation in the lake from 2005 to 2009, is associated with time interval from September 2007 to February 2009. This event was detected by XWT as a critical interval to be holding the strong correlation between the land subsidence phenomena and surface temperature. Eventually the analysis can be used for modeling and prediction purposes and probably stave off the damage from subsidence phenomena.

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Copernicus Sentinel-1 MT-InSAR, GNSS and Seismic Monitoring of Deformation Patterns and Trends at the Methana Volcano, Greece

Applied Sciences ◽

10.3390/app10186445 ◽

2020 ◽

Vol 10 (18) ◽

pp. 6445 ◽

Cited By ~ 1

Author(s):

Theodoros Gatsios ◽

Francesca Cigna ◽

Deodato Tapete ◽

Vassilis Sakkas ◽

Kyriaki Pavlou ◽

...

Keyword(s):

Land Surface ◽

Surface Deformation ◽

Ground Deformation ◽

Local Population ◽

Seasonal Fluctuation ◽

Satellite System ◽

Deformation Monitoring ◽

Persistent Scatterers ◽

Geothermal Activity ◽

Global Navigation Satellite

The Methana volcano in Greece belongs to the western part of the Hellenic Volcanic Arc, where the African and Eurasian tectonic plates converge at a rate of approximately 3 cm/year. While volcanic hazard in Methana is considered low, the neotectonic basin constituting the Saronic Gulf area is seismically active and there is evidence of local geothermal activity. Monitoring is therefore crucial to characterize any activity at the volcano that could impact the local population. This study aims to detect surface deformation in the whole Methana peninsula based on a long stack of 99 Sentinel-1 C-band Synthetic Aperture Radar (SAR) images in interferometric wide swath mode acquired in March 2015–August 2019. A Multi-Temporal Interferometric SAR (MT-InSAR) processing approach is exploited using the Interferometric Point Target Analysis (IPTA) method, involving the extraction of a network of targets including both Persistent Scatterers (PS) and Distributed Scatterers (DS) to augment the monitoring capability across the varied land cover of the peninsula. Satellite geodetic data from 2006–2019 Global Positioning System (GPS) benchmark surveying are used to calibrate and validate the MT-InSAR results. Deformation monitoring records from permanent Global Navigation Satellite System (GNSS) stations, two of which were installed within the peninsula in 2004 (METH) and 2019 (MTNA), are also exploited for interpretation of the regional deformation scenario. Geological, topographic, and 2006–2019 seismological data enable better understanding of the ground deformation observed. Line-of-sight displacement velocities of the over 4700 PS and 6200 DS within the peninsula are from −18.1 to +7.5 mm/year. The MT-InSAR data suggest a complex displacement pattern across the volcano edifice, including local-scale land surface processes. In Methana town, ground stability is found on volcanoclasts and limestone for the majority of the urban area footprint while some deformation is observed in the suburban zones. At the Mavri Petra andesitic dome, time series of the exceptionally dense PS/DS network across blocks of agglomerate and cinder reveal seasonal fluctuation (5 mm amplitude) overlapping the long-term stable trend. Given the steepness of the slopes along the eastern flank of the volcano, displacement patterns may indicate mass movements. The GNSS, seismological and MT-InSAR analyses lead to a first account of deformation processes and their temporal evolution over the last years for Methana, thus providing initial information to feed into the volcano baseline hazard assessment and monitoring system.

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GPS-derived ground deformation (2005–2014) within the Gulf of Mexico region referred to a stable Gulf of Mexico reference frame

Natural Hazards and Earth System Science ◽

10.5194/nhess-16-1583-2016 ◽

2016 ◽

Vol 16 (7) ◽

pp. 1583-1602 ◽

Cited By ~ 11

Author(s):

Jiangbo Yu ◽

Guoquan Wang

Keyword(s):

Gulf Of Mexico ◽

Reference Frame ◽

Mexico City ◽

Ground Deformation ◽

Local Reference Frame ◽

Subsidence Rate ◽

Local Reference ◽

Houston Area ◽

Southeastern Louisiana

Abstract. This study investigates current ground deformation derived from the GPS geodesy infrastructure in the Gulf of Mexico region. The positions and velocity vectors of 161 continuous GPS (CGPS) stations are presented with respect to a newly established local reference frame, the Stable Gulf of Mexico Reference Frame (SGOMRF). Thirteen long-term (> 5 years) CGPS are used to realize the local reference frame. The root mean square (RMS) of the velocities of the 13 SGOMRF reference stations achieves 0.2 mm yr−1 in the horizontal and 0.3 mm yr−1 in the vertical directions. GPS observations presented in this study indicate significant land subsidence in the coastal area of southeastern Louisiana, the greater Houston metropolitan area, and two cities in Mexico (Aguascalientes and Mexico City). The most rapid subsidence is recorded at the Mexico City International airport, which is up to 26.6 cm yr−1 (2008–2014). Significant spatial variation of subsidence rates is observed in both Mexico City and the Houston area. The overall subsidence rate in the Houston area is decreasing. The subsidence rate in southeastern Louisiana is relatively smaller (4.0–6.0 mm yr−1) but tends to be steady over time. This poses a potential threat to the safety of coastal infrastructure in the long-term.

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An Advanced Multipath Mitigation Method Based on Trend Surface Analysis

Remote Sensing ◽

10.3390/rs12213601 ◽

2020 ◽

Vol 12 (21) ◽

pp. 3601

Author(s):

Zhiren Wang ◽

Wen Chen ◽

Danan Dong ◽

Chenglong Zhang ◽

Yu Peng ◽

...

Keyword(s):

Surface Analysis ◽

Low Cost ◽

Correction Method ◽

Satellite System ◽

Double Difference ◽

Trend Surface Analysis ◽

Multipath Mitigation ◽

Trend Surface ◽

Noise Interference ◽

Grid Points

Among various ways to eliminate the multipath effect in high-precision global navigation satellite system positioning, the multipath hemispherical map (MHM) is a typical multipath correction method based on spatial domain repeatability, which is suitable for not only static environments, but also some dynamic carriers, such as ships and aircraft. So, it has notable advantages and is widely used. The MHM method divides the sky into grids according to the azimuth and elevation angles of satellite, and calculates the average of the residuals within the grid points as its multipath calibration value. It is easy to implement, but it will inevitably lead to excessive or insufficient multipath correction in the grid. The trend surface analysis-based multipath hemispherical map (T-MHM) method makes up for this deficiency by performing trend surface analysis on the multipath spatial changes within the grid points. However, the effectiveness of T-MHM is limited and less capable of resisting noise interference due to the multicollinearity between the independent variables caused by the special spatial distribution of multipath sampling and the overfitting problem caused by ignoring the multipath anisotropy. Thus, we proposed an improved multipath elimination method named AT-MHM (advanced trend surface analysis-based multipath hemispherical model), which cautiously judges the occurrence of the above problems and gives corresponding solutions. This was extended to double-difference mode, which expands the scope of application. The performance of AT-MHM in GPS pseudorange multipath mitigation was verified on geodetic receiver and low-cost receiver in a strong multipath environment with high occlusion.

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Geodetic Study of the 2006–2010 Ground Deformation in La Palma (Canary Islands): Observational Results

Remote Sensing ◽

10.3390/rs12162566 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2566

Author(s):

Joaquín Escayo ◽

José Fernández ◽

Juan F. Prieto ◽

Antonio G. Camacho ◽

Mimmo Palano ◽

...

Keyword(s):

Canary Islands ◽

Surface Deformation ◽

Ground Deformation ◽

Satellite System ◽

Point Of View ◽

Synthetic Aperture Radar Interferometry ◽

La Palma ◽

Moderate Seismicity ◽

Definition Of ◽

Global Navigation Satellite

La Palma is one of the youngest of the Canary Islands, and historically the most active. The recent activity and unrest in the archipelago, the moderate seismicity observed in 2017 and 2018 and the possibility of catastrophic landslides related to the Cumbre Vieja volcano have made it strongly advisable to ensure a realistic knowledge of the background surface deformation on the island. This will then allow any anomalous deformation related to potential volcanic unrest on the island to be detected by monitoring the surface deformation. We describe here the observation results obtained during the 2006–2010 period using geodetic techniques such as Global Navigation Satellite System (GNSS), Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR) and microgravimetry. These results show that, although there are no significant associated variations in gravity, there is a clear surface deformation that is spatially and temporally variable. Our results are discussed from the point of view of the unrest and its implications for the definition of an operational geodetic monitoring system for the island.

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Characterisation of GNSS Carrier Phase Data on a Moving Zero-Baseline in Urban and Aerial Navigation

Sensors ◽

10.3390/s20144046 ◽

2020 ◽

Vol 20 (14) ◽

pp. 4046 ◽

Cited By ~ 2

Author(s):

Fabian Ruwisch ◽

Ankit Jain ◽

Steffen Schön

Keyword(s):

Global Navigation Satellite System ◽

Carrier Phase ◽

High Sensitivity ◽

Satellite System ◽

Double Difference ◽

Navigation Satellite ◽

Noise Levels ◽

Global Navigation ◽

Zero Baseline ◽

Global Navigation Satellite

We present analyses of Global Navigation Satellite System (GNSS) carrier phase observations in multiple kinematic scenarios for different receiver types. Multi-GNSS observations are recorded on high sensitivity and geodetic-grade receivers operating on a moving zero-baseline by conducting terrestrial urban and aerial flight experiments. The captured data is post-processed; carrier phase residuals are computed using the double difference (DD) concept. The estimated noise levels of carrier phases are analysed with respect to different parameters. We find DD noise levels for L1 carrier phase observations in the range of 1.4–2 mm (GPS, Global Positioning System), 2.8–4.6 mm (GLONASS, Global Navigation Satellite System), and 1.5–1.7 mm (Galileo) for geodetic receiver pairs. The noise level for high sensitivity receivers is at least higher by a factor of 2. For satellites elevating above 30 ∘ , the dominant noise process is white phase noise. For the flight experiment, the elevation dependency of the noise is well described by the exponential model, while for the terrestrial urban experiment, multipath and diffraction effects overlay; hence no elevation dependency is found. For both experiments, a carrier-to-noise density ratio (C/N 0 ) dependency for carrier phase DDs of GPS and Galileo is clearly visible with geodetic-grade receivers. In addition, C/N 0 dependency is also visible for carrier phase DDs of GLONASS with geodetic-grade receivers for the terrestrial urban experiment.

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25-Second Determination of 2019 Mw 7.1 Ridgecrest Earthquake Coseismic Deformation

Bulletin of the Seismological Society of America ◽

10.1785/0120200084 ◽

2020 ◽

Vol 110 (4) ◽

pp. 1680-1687 ◽

Cited By ~ 1

Author(s):

Timothy I. Melbourne ◽

Walter M. Szeliga ◽

V. Marcelo Santillan ◽

Craig W. Scrivner

Keyword(s):

Mojave Desert ◽

Seismic Waves ◽

Ground Deformation ◽

Cumulative Effect ◽

Satellite System ◽

Coseismic Deformation ◽

Fault Rupture ◽

Fault Creep ◽

Origin Time ◽

Rupture Duration

ABSTRACT We have developed a global earthquake monitoring system based on low-latency measurements from more than 1000 existing Global Navigational Satellite System (GNSS) receivers, of which nine captured the 2019 Mw 6.4 Ridgecrest, California, foreshock and Mw 7.1 mainshock earthquakes. For the foreshock, coseismic offsets of up to 10 cm are resolvable on one station closest to the fault, but did not trigger automatic offset detection. For the mainshock, GNSS monitoring determined its coseismic deformation of up to 70 cm on nine nearby stations within 25 s of event nucleation. These 25 s comprise the fault rupture duration itself (roughly 10 s of peak moment release), another 10 s for seismic waves and displacement to propagate to nearby GNSS stations, and a few additional seconds for surface waves and other crustal reverberations to dissipate sufficiently such that coseismic offset estimation filters could reconverge. Latency between data acquisition in the Mojave Desert and positioning in Washington State averaged 1.4 s, a small fraction of the fault rupture time itself. GNSS position waveforms for the two closest stations that show the largest dynamic and static displacements agree well with postprocessed time series. Mainshock coseismic ground deformation estimated within 25 s of origin time also agrees well with, but is ∼10% smaller than, deformation estimated using 48 hr observation windows, which may reflect rapid postseismic fault creep or the cumulative effect of nearly 1000 aftershocks in the 48 hr following the mainshock. GNSS position waveform shapes, which comprise a superposition of dynamic and static displacements, are well modeled by frequency–wavenumber synthetics for the Hadley–Kanamori 1D crustal structure model and the U.S. Geological Survey finite-rupture distribution and timing. These results show that GNSS seismic monitoring performed as designed and offers a new means of rapidly characterizing large earthquakes globally.

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