Slip Complementarity and Triggering between the Foreshock, Mainshock, and Afterslip of the 2019 Ridgecrest Rupture Sequence

ABSTRACT We investigate the deformation processes during the 2019 Ridgecrest earthquake sequence by combining Global Navigation Satellite Systems, strong-motion, and Interferometric Synthetic Aperture Radar datasets in a joint inversion. The spatial complementarity of slip between the Mw 6.4 foreshock, Mw 7.1 mainshock, and afterslip suggests the importance of static stress transfer as a triggering mechanism during the rupture sequence. The coseismic slip of the foreshock concentrates mainly on the east-northeast–west-southwest fault above the hypocenter at depths of 2–8 km. The slip distribution of the mainshock straddles the region above the hypocenter with two isolated patches located to the north-northwest and south-southeast, respectively. The geodetically determined moment magnitudes of the foreshock and mainshock are equivalent to moment magnitudes Mw 6.4 and 7.0, assuming a rigidity of 30 GPa. We find a significant shallow slip deficit (>60%) in the Ridgecrest ruptures, likely resulting from the immature fault system in which the sequence occurred. Rapid afterslip concentrates at depths of 2–6 km, surrounding the rupture areas of the foreshock and mainshock. The ruptures also accelerated viscoelastic flow at lower-crustal depths. The Garlock fault was loaded at several locations, begging the question of possible delayed triggering.

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Seismic and Geodetic Analysis of Rupture Characteristics of the 2020 Mw 6.5 Monte Cristo Range, Nevada, Earthquake

Bulletin of the Seismological Society of America ◽

10.1785/0120200327 ◽

2021 ◽

Author(s):

Chengli Liu ◽

Thorne Lay ◽

Fred F. Pollitz ◽

Jiao Xu ◽

Xiong Xiong

Keyword(s):

Surface Deformation ◽

Joint Inversion ◽

Complex Surface ◽

Global Navigation Satellite Systems ◽

Fault System ◽

Satellite Systems ◽

Walker Lane ◽

Global Navigation Satellite ◽

Mina Deflection ◽

East West

ABSTRACT The largest earthquake since 1954 to strike the state of Nevada, United States, ruptured on 15 May 2020 along the Monte Cristo range of west-central Nevada. The Mw 6.5 event involved predominantly left-lateral strike-slip faulting with minor normal components on three aligned east–west-trending faults that vary in strike by 23°. The kinematic rupture process is determined by joint inversion of Global Navigation Satellite Systems displacements, Interferometric Synthetic Aperture Radar (InSAR) data, regional strong motions, and teleseismic P and SH waves, with the three-fault geometry being constrained by InSAR surface deformation observations, surface ruptures, and relocated aftershock distributions. The average rupture velocity is 1.5 km/s, with a peak slip of ∼1.6 m and a ∼20 s rupture duration. The seismic moment is 6.9×1018 N·m. Complex surface deformation is observed near the fault junction, with a deep near-vertical fault and a southeast-dipping fault at shallow depth on the western segment, along which normal-faulting aftershocks are observed. There is a shallow slip deficit in the Nevada ruptures, probably due to the immature fault system. The causative faults had not been previously identified and are located near the transition from the Walker Lane belt to the Basin and Range province. The east–west geometry of the system is consistent with the eastward extension of the Mina Deflection of the Walker Lane north of the White Mountains.

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Assessment of Empirical Troposphere Model GPT3 Based on NGL’s Global Troposphere Products

Sensors ◽

10.3390/s20133631 ◽

2020 ◽

Vol 20 (13) ◽

pp. 3631

Author(s):

Junsheng Ding ◽

Junping Chen

Keyword(s):

Global Navigation Satellite Systems ◽

Tropospheric Delay ◽

Strongly Correlated ◽

International Gnss Service ◽

Total Delay ◽

Average Deviation ◽

Satellite Systems ◽

Global Average ◽

The North ◽

Global Navigation Satellite

Tropospheric delay is one of the major error sources in GNSS (Global Navigation Satellite Systems) positioning. Over the years, many approaches have been devised which aim at accurately modeling tropospheric delays, so-called troposphere models. Using the troposphere data of over 16,000 global stations in the last 10 years, as calculated by the Nevada Geodetic Laboratory (NGL), this paper evaluates the performance of the empirical troposphere model GPT3, which is the latest version of the GPT (Global Pressure and Temperature) series model. Owing to the large station number, long time-span and diverse station distribution, the spatiotemporal properties of the empirical model were analyzed using the average deviation (BIAS) and root mean square (RMS) error as indicators. The experimental results demonstrate that: (1) the troposphere products of NGL have the same accuracy as the IGS (International GNSS Service) products and can be used as a reference for evaluating general troposphere models. (2) The global average BIAS of the ZTD (zenith total delay) estimated by GPT3 is −0.99 cm and the global average RMS is 4.41 cm. The accuracy of the model is strongly correlated with latitude and ellipsoidal height, showing obviously seasonal variations. (3) The global average RMS of the north gradient and east gradient estimated by GPT3 is 0.77 mm and 0.73 mm, respectively, which are strongly correlated with each other, with values increasing from the equator to lower latitudes and decreasing from lower to higher latitudes.

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Joint Inversion of Rupture across a Fault Stepover during the 8 August 2017 Mw 6.5 Jiuzhaigou, China, Earthquake

Seismological Research Letters ◽

10.1785/0220210084 ◽

2021 ◽

Author(s):

Yong Zhang ◽

Wanpeng Feng ◽

Xingxing Li ◽

Yajing Liu ◽

Jieyuan Ning ◽

...

Keyword(s):

Joint Inversion ◽

Strong Motion ◽

Focal Mechanisms ◽

High Rate ◽

Fault System ◽

Interferometric Synthetic Aperture Radar ◽

Coseismic Slip ◽

Jiuzhaigou Earthquake ◽

Rupture Model ◽

The Right

Abstract The 8 August 2017 Mw 6.5 Jiuzhaigou earthquake occurred in a tectonically fractured region in southwest China. We investigate the multifault coseismic rupture process by jointly analyzing teleseismic, strong-motion, high-rate Global Positioning System, and Interferometric Synthetic Aperture Radar (InSAR) datasets. We clearly identify two right-stepping fault segments and a compressional stepover based on variations in focal mechanisms constrained by coseismic InSAR deformation data. The average geometric parameters of the northwest and southeast segments are strike = 130°/dip = 57° and strike = 151°/dip = 70°, respectively. The rupture model estimated from a joint inversion of the seismic and geodetic datasets indicates that the rupture initiated on the southeastern segment and jumped to the northwestern segment, resulting in distinctive slip patches on the two segments. A 4-km-long coseismic slip gap was identified around the stepover, consistent with the aftershock locations and mechanisms. The right-stepping segmentation and coseismic rupture across the compressional stepover exhibited by the 2017 Jiuzhaigou earthquake are reminiscent of the multifault rupture pattern during the 1976 Songpan earthquake sequence farther south along the Huya fault system in three successive Ms∼7 events. Although the common features of fault geometry and stepover may control the similarity in event locations and focal mechanisms of the 2017 and 1976 sequences, the significantly wider (~15 km) stepover in the 1976 sequence likely prohibited coseismic rupture jumping and hence reduced seismic hazard.

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The contribution of engineering surveys by means of GPS to the determination of crustal movements in Istanbul

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-1705-2011 ◽

2011 ◽

Vol 11 (6) ◽

pp. 1705-1713 ◽

Cited By ~ 4

Author(s):

M. Özyaşar ◽

M. T. Özlüdemir

Keyword(s):

Positional Information ◽

Global Navigation Satellite Systems ◽

Marmara Region ◽

Satellite Systems ◽

Geodetic Networks ◽

The North ◽

Richter Scale ◽

Tectonically Active ◽

Vertical Displacements ◽

Global Navigation Satellite

Abstract. Global Navigation Satellite Systems (GNSS) are space based positioning techniques and widely used in geodetic applications. Geodetic networking accomplished by engineering surveys constitutes one of these tasks. Geodetic networks are used as the base of all kinds of geodetic implementations, Co from the cadastral plans to the relevant surveying processes during the realization of engineering applications. Geodetic networks consist of control points positioned in a defined reference frame. In fact, such positional information could be useful for other studies as well. One of such fields is geodynamic studies that use the changes of positions of control stations within a network in a certain time period to understand the characteristics of tectonic movements. In Turkey, which is located in tectonically active zones and struck by major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. For this purpose, a GPS (Global Positioning System) network of 650 stations distributed over Istanbul (Istanbul GPS Triangulation Network; abbreviated IGNA) covering the northern part of the North Anatolian Fault Zone (NAFZ) was established in 1997 and measured in 1999. From 1998 to 2004, the IGNA network was extended to 1888 stations covering an area of about 6000 km2, the whole administration area of Istanbul. All 1888 stations within the IGNA network were remeasured in 2005. In these two campaigns there existed 452 common points, and between these two campaigns two major earthquakes took place, on 17 August and 12 November 1999 with a Richter scale magnitude of 7.4 and 7.2, respectively. Several studies conducted for estimating the horizontal and vertical displacements as a result of these earthquakes on NAFZ are discussed in this paper. In geodynamic projects carried out before the earthquakes in 1999, an annual average velocity of 2–2.5 cm for the stations along the NAFZ were estimated. Studies carried out using GPS observations in the same area after these earthquakes indicated that point displacements vary depending on their distance to the epicentres of the earthquakes. But the directions of point displacements are similar. The results obtained through the analysis of the IGNA network also show that there is a common trend in the directions of point displacements in the study area. In this paper, the past studies about the tectonics of Marmara region are summarised and the results of the displacement analysis on the IGNA network are discussed.

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Estimating Wave Direction by Using Terrestrial GNSS Reflectometry

10.20944/preprints201904.0081.v1 ◽

2019 ◽

Author(s):

Jörg Reinking ◽

Ole Roggenbuck ◽

Gilad Even-Tzur

Keyword(s):

Correlation Length ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Global Navigation Satellite Systems ◽

Wave Direction ◽

Satellite Systems ◽

The North ◽

Scattered Power ◽

Length Changes ◽

Global Navigation Satellite

The signal-to-noise ratio (SNR) data is part of the global navigation satellite systems (GNSS) observables. In a marine environment, the oscillation of the SNR data can be used to derive reflector heights. Since the attenuation of the SNR oscillation is related to the roughness of the sea surface, the significant wave height (SWH) of the water surface can be calculated from the analysis of the attenuation. The attenuation depends additionally on the relation between the coherent and the incoherent part of the scattered power. The latter is a function of the correlation length of the surface waves. Because the correlation length changes with respect to the direction of the line of sight relative to the wave direction, the attenuation must show an anisotropic characteristic. In this work, we present a method to derive the wave direction from the anisotropy of the attenuation of the SNR data. The method is investigated based on simulated data as well by the analysis of experimental data from a GNSS station in the North Sea.

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Migrating from ATS77 to NAD83(CSRS) in Nova Scotia

GEOMATICA ◽

10.5623/cig2017-201 ◽

2017 ◽

Vol 71 (2) ◽

pp. 75-87

Author(s):

Jason Bond

Keyword(s):

Nova Scotia ◽

Global Navigation Satellite Systems ◽

Transformation Model ◽

Mapping Data ◽

Satellite Systems ◽

Spatial Reference ◽

The North ◽

Coordinate Control ◽

Original Size ◽

Global Navigation Satellite

Since the late 1970s, the foundation for all survey work in Nova Scotia has been the Nova Scotia Coordinate Control System (NSCCS), which is based upon the Average Terrestrial System of 1977 (ATS77). In the early 2000s, some provincial mapping layers were migrated to the North American Datum of 1983 (based upon the Canadian Spatial Reference System (NAD83(CSRS)), but many still utilize ATS77. In 2012, the province began modernizing its Coordinate Referencing program using Global Navigation Satellite Systems (GNSS) and imple menting Active Control Stations (ACSs). The installation of 40 ACSs across the province between 2012 and 2015 enables the surveying community in Nova Scotia to migrate to NAD83(CSRS) by addressing ongoing accuracy and accessibility needs. The tech nology has allowed the passive, NAD83(CSRS)-based, Nova Scotia High Precision Network to expand to more than five times its original size. This densification effort has also allowed the transformation model between the two datums to be enhanced. With the geodetic infrastructure in place, the current primary need is for knowledge and methodologies to facilitate the transition. Two options are presented to aid surveyors and mappers in migrating data from ATS77 to NAD83(CSRS). The first approach utilizes a newly developed grid shift file intended for transforming mapping data and aiding surveyors in relocating boundary evidence, so that it can then be remeasured in NAD83(CSRS). A detailed discussion is provided on the development of grid shift file. The second approach is based upon the derivation of a set of local transformation parameters using a one-to-one sampling of the control monuments used in the historic survey.

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Magnitude Calculation without Saturation from Strong-Motion Waveforms

Bulletin of the Seismological Society of America ◽

10.1785/0120200133 ◽

2020 ◽

Author(s):

Zhang Hongcai ◽

Diego Melgar ◽

Dara E. Goldberg

Keyword(s):

Real Time ◽

Near Field ◽

Magnitude Estimate ◽

Strong Motion ◽

Global Navigation Satellite Systems ◽

Coseismic Deformation ◽

Ground Displacement ◽

Strong Motion Records ◽

Satellite Systems ◽

Global Navigation Satellite

ABSTRACT After destructive earthquakes, it is a challenge to estimate magnitude rapidly and accurately for dissemination to emergency responders and the public. Here, we propose criteria to calculate peak ground displacement (PGD) from strong-motion records, which can be used to calculate unsaturated event magnitude. Using collocated strong-motion and Global Navigation Satellite Systems observations of five major earthquakes in Japan, we demonstrate the effectiveness and accuracy of our strategy. Our results show that, with the right filtering criteria, PGD estimated from strong-motion acceleration waveforms is consistent with geodetic estimates. The methodology, however, does not allow for calculation of reliable estimates of coseismic deformation or other ground displacement metrics. We demonstrate a simulated real-time magnitude estimation that suggests it is feasible to generate an unsaturated magnitude estimate in real time from near-field strong-motion records. These findings have important implications for early warning and emergency response in seismically active areas, especially where real-time strong-motion data are more widely available than geodetic measurements.

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Estimating Wave Direction Using Terrestrial GNSS Reflectometry

Remote Sensing ◽

10.3390/rs11091027 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1027 ◽

Cited By ~ 1

Author(s):

Reinking ◽

Roggenbuck ◽

Even-Tzur

Keyword(s):

Correlation Length ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Global Navigation Satellite Systems ◽

Wave Direction ◽

Satellite Systems ◽

The North ◽

Scattered Power ◽

Length Changes ◽

Global Navigation Satellite

The signal-to-noise ratio (SNR) data are part of the global navigation satellite systems (GNSS) observables. In a marine environment, the oscillation of the SNR data can be used to derive reflector heights. Since the attenuation of the SNR oscillation is related to the roughness of the sea surface, the significant wave height (SWH) of the water surface can be calculated from the analysis of the attenuation. The attenuation depends additionally on the relation between the coherent and the incoherent part of the scattered power. The latter is a function of the correlation length of the surface waves. Since the correlation length changes with respect to the direction of the line of sight relative to the wave direction, the attenuation must show an anisotropic characteristic. In this work, we present a method to derive the wave direction from the anisotropy of the attenuation of the SNR data. The method is investigated based on simulated data, as well by the analysis of experimental data from a GNSS station in the North Sea.

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Automatic Extraction of Permanent Ground Offset from Near-Field Accelerograms: Algorithm, Validation, and Application to the 2004 Parkfield Earthquake

Bulletin of the Seismological Society of America ◽

10.1785/0120200040 ◽

2020 ◽

Vol 110 (6) ◽

pp. 2638-2646

Author(s):

Asaf Inbal ◽

Alon Ziv

Keyword(s):

Near Field ◽

Strong Motion ◽

Fault Slip ◽

Global Navigation Satellite Systems ◽

New Approach ◽

Satellite Systems ◽

Spatial Coverage ◽

Parkfield Earthquake ◽

Seismic Moment Release ◽

Global Navigation Satellite

ABSTRACT Permanent ground offsets, constituting a prime dataset for constraining final fault-slip distributions, may not be recovered straightforwardly by double integration of near-field accelerograms due to tilt and other distorting effects. Clearly, if a way could be found to recover permanent ground offsets from acceleration records, then static datasets would be enlarged, and thus the resolution of fault-slip inversions would be enhanced. Here, we introduce a new approach for extracting permanent offsets from near-field strong-motion accelerograms. The main advantage of the new approach with respect to previous ones is that it corrects for source time functions of any level of complexity. Its main novelty is the addition of a constraint on the slope of the ground velocity spectra at long periods. We validated the new scheme using collocated accelerograms and Global Navigation Satellite Systems (GNSS) records of the 2011 Mw 9 Tohoku-Oki earthquake. We find a good agreement between accelerogram-based and GNSS-based ground offsets over a range of 0.1–5 m. To improve the spatial coverage of permanent ground offsets associated with the 2004 Parkfield earthquake, near-field accelerograms were baseline corrected using the new scheme. Static slip inversion of the combined GNSS-based and accelerogram-based ground displacements indicates appreciable seismic moment release south of the epicenter, about 5 km into the Cholame section of the San Andreas fault. We conclude that the strong shaking observed to the south of the epicenter is directly related to the slip in that area and is not the result of local amplification.

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