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The Mw 6.2 Mamuju-Majene earthquake occurred on 14 January 2021, with the epicenter at 118.890°E, 2.972°S. The shaking caused severe damage in West Sulawesi, especially in the Mamuju and Majene cities. Most of the coseismic slip distribution of the Mamuju-Majene Earthquake is derived from the daily solutions, which might include early postseismic deformation. Therefore, we conducted a coseismic slip model using kinematic solution based on Global Navigation Satellite System (GNSS) to determine the best coseismic slip values and model distribution. Our analysis indicates that the coseismic displacement from the kinematic solution is higher than the static solution. The GNSS data was utilized for inversion analysis, considering two potential fault sources, they are the Makassar Strait Central Fault and the Mamuju Fault. We found a larger misfit between the observed data and the model generated on static and kinematic solutions along the Makassar Strait Central Fault. Based on the kinematic solution, the coseismic slip distribution represents that fault rupture spreading along a north-south orientation, while the static solution is centered in the northern part. The maximum coseismic slip from each kinematic and static solution is 0.29 m and 0.11 m, respectively. Meanwhile, the seismic moment generated from the kinematic solution is 1.5 × 1026 N m (equivalent to Mw 6.75), which is greater than the static solution of 2.4 × 1025 N m (equivalent to Mw 6.22). [ABSTRACT FROM AUTHOR]

Using high-rate (1 Hz) global positioning system (GPS) data, coseismic displacement estimates are obtained for the 2023 Mw 7.8 Pazarcik and Elbistan Mw 7.5 Türkiye earthquakes. The estimated largest displacements caused by the Mw 7.8 event are observed at station ante with an eastward component displacement of 31cm and at station mly1 with a southward component displacement of 39cm. The displacements caused by the Mw 7.8 Pazarcik event show left-lateral displacements along the nodal plane, which is consistent with the focal mechanism. The largest displacements caused by the Mw 7.5 event are a westward component displacement of 450 cm and a northward component displacement of 97cm at the station ekz1 which is only 6 km from the epicenter of the event. Based on high-rate GPS time series, the surface wave propagation of the Mw 7.8 Elbistan earthquake is preliminarily estimated at an overall speed of approximately 2.9 km/s, with a slightly higher speed of 3.1 km/s along the northeast direction and 3.0 km/s along the east direction. High-rate GPS measurements show a prominent advantage of temporal resolution for earthquake sequences with short intervals, and preliminary displacement estimates could be made with only a few hours of observations. The displacement estimation provides constraints for the inversion of the rupture process and seismic source mechanisms. [ABSTRACT FROM AUTHOR]

A strong motion seismometer is a kind of inertial sensor, and it can record middle- to high-frequency ground accelerations. The double-integration from acceleration to displacement amplifies errors caused by tilt, rotation, hysteresis, non-linear instrument response, and noise. This leads to long-period, non-physical baseline drifts in the integrated displacements. GNSS enables the direct observation of the ground displacements, with an accuracy of several millimeters to centimeters and a sample rate of 1 Hz to 50 Hz. Combining GNSS and a strong motion seismometer, one can obtain an accurate displacement series. Typically, a Kalman filter is adopted to integrate GNSS displacements and strong motion accelerations, using the empirical values of noise uncertainty. Considering that there are significantly different errors introduced by the above-mentioned tilt, rotation, hysteresis, and non-linear instrument response at different stations or at different times at the same station, it is inappropriate to employ a fixed noise uncertainty for strong motion accelerations. In this paper, we present a Sage–Husa Kalman filter, where the noise uncertainty of strong motion acceleration is adaptively estimated, to integrate GNSS and strong motion acceleration for obtaining the displacement series. The performance of the proposed method was validated by a shake table simulation experiment and the GNSS/strong motion co-located stations collected during the 2023 Mw 7.8 and Mw 7.6 earthquake doublet in southeast Turkey. The experimental results show that the proposed method enhances the adaptability to the variation of strong motion accelerometer noise level and improves the precision of integrated displacement series. The displacement derived from the proposed method was up to 28% more accurate than those from the Kalman filter in the shake table test, and the correlation coefficient with respect to the references arrived at 0.99. The application to the earthquake event shows that the proposed method can capture seismic waveforms at a promotion of 46% and 23% in the horizontal and vertical directions, respectively, compared with the results of the Kalman filter. [ABSTRACT FROM AUTHOR]

Retrieving the coseismic displacement in real time is essential when the high-rate Global Navigation Satellite System (GNSS) is used for the real-time earthquake source description. In 2020, the third generation of the BeiDou Global Navigation Satellite System (BDS-3) initiated a real-time precise point positioning service through the B2b signal (PPP-B2b), which provides a new possibility for real-time earthquake source description. In this study, the performance of the PPP-B2b on the real-time retrieval of coseismic displacement was first validated with GNSS observations collected during the 2021 Mw 7.4 Maduo earthquake. Then, the warning magnitude, focal mechanism and fault slip distribution were inverted with the derived PPP-B2b displacement in a simulated real-time model. Our results indicate that the accuracies of the coseismic displacements in the north, east and up components are 0.8 cm, 0.5 cm, and 1.4 cm for the single GPS PPP-B2b, 0.5 cm, 0.6 cm, and 0.9 cm for the single BDS-3 PPP-B2b and 0.4 cm, 0.3 cm, and 0.4 cm for the combined GPS/BDS-3 PPP-B2b, respectively, when compared with the coseismic displacements of the post-processing precise point positioning (PPP). Moreover, the warning magnitude, focal mechanism and fault slip distribution inverted with the PPP-B2b displacements are all in good agreement with those inverted with the PPP displacements. This study highlights the great possibility of the PPP-B2b to be used for earthquake early warning and rapid emergency responses. [ABSTRACT FROM AUTHOR]

A strong motion seismometer is a kind of inertial sensor, and it can record middle- to high-frequency ground accelerations. The double-integration from acceleration to displacement amplifies errors caused by tilt, rotation, hysteresis, non-linear instrument response, and noise. This leads to long-period, non-physical baseline drifts in the integrated displacements. GNSS enables the direct observation of the ground displacements, with an accuracy of several millimeters to centimeters and a sample rate of 1 Hz to 50 Hz. Combining GNSS and a strong motion seismometer, one can obtain an accurate displacement series. Typically, a Kalman filter is adopted to integrate GNSS displacements and strong motion accelerations, using the empirical values of noise uncertainty. Considering that there are significantly different errors introduced by the above-mentioned tilt, rotation, hysteresis, and non-linear instrument response at different stations or at different times at the same station, it is inappropriate to employ a fixed noise uncertainty for strong motion accelerations. In this paper, we present a Sage–Husa Kalman filter, where the noise uncertainty of strong motion acceleration is adaptively estimated, to integrate GNSS and strong motion acceleration for obtaining the displacement series. The performance of the proposed method was validated by a shake table simulation experiment and the GNSS/strong motion co-located stations collected during the 2023 Mw 7.8 and Mw 7.6 earthquake doublet in southeast Turkey. The experimental results show that the proposed method enhances the adaptability to the variation of strong motion accelerometer noise level and improves the precision of integrated displacement series. The displacement derived from the proposed method was up to 28% more accurate than those from the Kalman filter in the shake table test, and the correlation coefficient with respect to the references arrived at 0.99. The application to the earthquake event shows that the proposed method can capture seismic waveforms at a promotion of 46% and 23% in the horizontal and vertical directions, respectively, compared with the results of the Kalman filter.

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Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The epicenter, origin time, and magnitude of the earthquake are critical earthquake source parameters, as they can provide data support for earthquake emergency rescue and earthquake risk research, among others. Here, the high-rate displacement time series of 11 Global Navigation Satellite System (GNSS) stations during the 2022 Menyuan M6.9 earthquake were acquired using GPS, GPS/GLONASS, and GPS/GLONASS/Galileo observations using the PRIDE PPP-AR software. Our analysis revealed that the root mean squares (RMS) of displacement derived from GPS/GLONASS/Galileo relative to GPS-derived in the north, east, and up components were improved by 23.3, 34.4, and 24.4%, respectively. The epicenter location of the Menyuan earthquake based on GPS/GLONASS/Galileo-derived time series of each station was 101.201°E and 37.791°N, the earthquake origin time was 17:45:23.7 (UTC), and the moment magnitude was 6.62, which were more accurate than the GPS and GPS/GLONASS results. Although there was no significant advantage of calculating the coseismic displacement by multi-day static solution from GPS/GLONASS/Galileo, our results showed that the multi-GNSS combination can improve the stability of time series and reduce noise, and more realistically describe the surface displacement changes during earthquakes; accuracy of earthquake source parameters estimation, can, therefore, be improved with the use of multi-GNSS data. [ABSTRACT FROM AUTHOR]

The current prototype of a fully automatic earthquake tsunami hazard assessment system, "Tsunami Observer", is described. The transition of the system to the active phase of operation occurs when information about a strong earthquake (Mw ≥ 6.0) is received. In the first stage, the vector field of coseismic displacements of the Earth's crust is calculated by using the Okada formulas. In the calculations, use is made of data on the coordinates, the seismic moment, the focal mechanism, and the depth of the earthquake, as well as empirical patterns. In the second stage, the initial elevation of the water surface at the tsunami's focus is determined with the vector field of coseismic displacements of the bottom and the distribution of ocean depths, and the earthquake's potential energy is calculated. In the third stage, the intensity of the tsunami is estimated on the Soloviev–Imamura scale in accordance with the magnitude of the potential energy by using the empirical relationship that is obtained as a result of a statistical analysis of historical tsunami events. In the final stage, if the energy exceeds the critical value of 109 J, a numerical simulation of the tsunami is performed, which allows the determination of the predominant directions of wave energy propagation and estimation of the runup height on the nearest coast. In this work, data on the operation of the system over the last 3 years are presented. [ABSTRACT FROM AUTHOR]

Focusing on stratified tropospheric delay correction in the small-amplitude coseismic displacement field of small-to-moderate earthquakes (

Coseismic displacements estimated from comparison before-and-after satellite images suggest that the large and intermittently active landslide upon which the village of Laprak, Nepal, was built moved a geometric mean of 80 cm (95% mean confidence interval of 74–86 cm) or less during the 2015 Mw 7.8 Gorkha earthquake. The village was located about 6 km from the earthquake epicenter. We used published geotechnical and topographic data collected as part of a previous study of the landslide, publicly available earthquake information, and a physically plausible range of pre-monsoon dry season pore-pressure coefficients to constrain Monte Carlo simulations based on six published simplified Newmark models of coseismic displacement in natural slopes. Kolmogorov–Smirnov statistics show that five of the models produced coseismic displacement distributions in good to marginal agreement with our satellite image measurements. A seventh result obtained by combining results from the six individual models to balance the strengths and weaknesses of each also produced good agreement. The agreement between our observed and simulated results suggests that simplified Newmark models may be reliable tools for reconnaissance level earthquake hazard assessment in mountainous areas if probabilistic approaches are used to account for input parameter uncertainty. [ABSTRACT FROM AUTHOR]

Studies on cases of more than 10 strong earthquakes of M6.0 to M9.0 since the 2008 Wenchuan earthquake around the world with GPS observations and crustal deformation precursors are reviewed. These earthquakes occurred in regions of different tectonic movements and of different types. They are the M8.0 Wenchuan earthquake in 2008，the M9.0 Tohoku earthquake in 2011 in Japan，the M7.0 Lushan earthquake in 2013 and so on until the recent earthquake of M7.4 in Mexico in Jun., 2020 and the southern Alaska offshore earthquake of M7.8 in Jul.，2020. Based on the time series of horizontal displacement components and horizontal displacement field，particularly the time series of horizontal displacement vectors，in the regional reference frames，studies have shown that the coseismic displacements are the keys to the confirmation of the existence of crustal deformations precursory to earthquakes. The time series of vertical displacements and horizontal displacement vectors，the coseismic vertical displacements and decomposition of the coseismic horizontal displacement vectors have revealed the real pattern of elastic rebound. A model of rebound or elastic rebound of (preseismic) compression-(coseismic) shear strain is proposed in agreement with results of rock failure tests and the GPS observations. Based on the studies of the earthquake cases，a layout of stations of continuous GNSS observations of monitoring precursory crustal deformations for possible predictions of earthquakes of different magnitudes is proposed.

Abstract Surface displacements associated with earthquake-cycle deformation of active faults significantly influence the accuracy of geodetic datum and reference frames, especially for the Taiwan area with high plate convergence and deformation rates. Following the current architecture of the semi-kinematic reference frame in Taiwan, which does not particularly consider the non-linear behavior of postseismic deformation, we explored the methods to implement a non-linear postseismic deformation model using the 2003 Chengkung earthquake as an example. Together with linear interseismic function, we utilized a logarithmic function to approximate the non-linear postseismic decays. For the time series without preseismic observations, we removed the interseismic velocities by spatial interpolation and fitted the resultant time series with the logarithmic function. After estimating postseismic decays for all GPS stations, we conducted two grid models of accumulative displacements for only postseismic deformation and total deformation after the earthquake. The first grid model provides a useful prediction for tracking surface movements, and the latter model provides a straightforward view to access the timing and amount of displacements to correct the semi-kinematic reference frame. The implementation of the grid models can well approximate non-linear postseismic trends for the semi-kinematic reference frame.

The current prototype of a fully automatic earthquake tsunami hazard assessment system, “Tsunami Observer”, is described. The transition of the system to the active phase of operation occurs when information about a strong earthquake (Mw ≥ 6.0) is received. In the first stage, the vector field of coseismic displacements of the Earth’s crust is calculated by using the Okada formulas. In the calculations, use is made of data on the coordinates, the seismic moment, the focal mechanism, and the depth of the earthquake, as well as empirical patterns. In the second stage, the initial elevation of the water surface at the tsunami’s focus is determined with the vector field of coseismic displacements of the bottom and the distribution of ocean depths, and the earthquake’s potential energy is calculated. In the third stage, the intensity of the tsunami is estimated on the Soloviev–Imamura scale in accordance with the magnitude of the potential energy by using the empirical relationship that is obtained as a result of a statistical analysis of historical tsunami events. In the final stage, if the energy exceeds the critical value of 109 J, a numerical simulation of the tsunami is performed, which allows the determination of the predominant directions of wave energy propagation and estimation of the runup height on the nearest coast. In this work, data on the operation of the system over the last 3 years are presented.

The determination of crustal deformation can be measured by geodetic observations of permanent global positioning system (GPS) stations. In this study, the coseismic displacement of 11 August 2012 with magnitudes 6.5 Mw and 6.3 Mw of Ahar–Varzegan earthquakes has been investigated based on GPS observations and deep learning. For this purpose, data were processed at a 30-s rate of 13 Iran geodynamic stations with distances of 25 to 160 km from the earthquake epicenter and then were entered into deep learning. The results show that the horizontal displacement field of the Ahar–Varzegan earthquake has a mean value of 27.93 cm and 15.35 cm, which is estimated with the root mean square error (RMSE) of ±0.24 cm. Vertical displacement has been neglected due to the low accuracy of the z component and the low density of stations in the central seismic range. Also, the right lateral fault (cause of Ahar–Varzegan earthquake) to seismic displacement is evident; field observations and previous research confirm coseismic displacement values and right latera fault. [ABSTRACT FROM AUTHOR]

High-rate GNSS technology is invaluable for capturing surface displacements. However, vertical displacement is strongly linked to zenith tropospheric delay (ZTD) and receiver clock bias, compromising accuracy and impeding the detection of weak seismic waves. Some GNSS stations, fortunately, feature high-stability oscillators, enabling receiver clock modeling instead of epoch-wise estimation. This paper introduces an epoch relative positioning approach (ERP)with receiver clock modeling (CMC-ERP) to enhance coseismic displacement accuracy. Applied to earthquakes in Japan and the United States, the method improves vertical displacement accuracy by 24% to 61%. Furthermore, P-wave arrival times are determined by processing displacement sequences extracted through both CMC-ERP and ERP methods using STA/LTA. Compared to theoretical arrival times calculated by TauP software, CMC-ERP accuracy is enhanced by 74%–99%, further confirming its effectiveness. • GPS receiver clock modeling is considered to improve the accuracy of dynamic coseismic displacement solution. • A new GPS-extracted coseismic displacement model with clock modeling constraint is constructed. • Further improvement of vertical displacement accuracy and extraction of P-wave arrivals through specific seismic case validation. [ABSTRACT FROM AUTHOR]

Abstract A fundamental topic in earthquake studies is understanding the extent to which fault rupture at the surface is localized on primary fault strands as opposed to distributed tens to hundreds of meters away from primary ruptures through off‐fault deformation (OFD) via a combination of discrete secondary faulting and bulk deformation. The 2019 Ridgecrest, CA Mw6.4 and Mw7.1 earthquakes provide an opportunity to explore this problem via comparison of published field‐based and mostly on‐fault offset measurements, with new lateral displacement measurements made over length scales of hundreds of meters across the primary rupture using WorldView satellite images collected before and after the earthquakes. A mean fit to the field observations underestimates net slip (pixel‐correlation results) by an average of 0.4 m along the Mw6.4 rupture (∼41% of net left‐lateral displacement) and 0.7 m along the Mw7.1 rupture (∼65% of net right‐lateral displacement). We attribute these differences to substantial OFD along the lengths of the Mw6.4 (∼59%) and Mw7.1 (∼35%) ruptures. A maximum fit to the field observations provides an improved match to the pixel correlation results (difference of 0.1–0.2 m or ∼76%–98% of net displacement). OFD may in part depend on displacement magnitude, where locations along the rupture with smaller displacements (

A fundamental topic in earthquake studies is understanding the extent to which fault rupture at the surface is localized on primary fault strands as opposed to distributed tens to hundreds of meters away from primary ruptures through off‐fault deformation (OFD) via a combination of discrete secondary faulting and bulk deformation. The 2019 Ridgecrest, CA Mw6.4 and Mw7.1 earthquakes provide an opportunity to explore this problem via comparison of published field‐based and mostly on‐fault offset measurements, with new lateral displacement measurements made over length scales of hundreds of meters across the primary rupture using WorldView satellite images collected before and after the earthquakes. A mean fit to the field observations underestimates net slip (pixel‐correlation results) by an average of 0.4 m along the Mw6.4 rupture (∼41% of net left‐lateral displacement) and 0.7 m along the Mw7.1 rupture (∼65% of net right‐lateral displacement). We attribute these differences to substantial OFD along the lengths of the Mw6.4 (∼59%) and Mw7.1 (∼35%) ruptures. A maximum fit to the field observations provides an improved match to the pixel correlation results (difference of 0.1–0.2 m or ∼76%–98% of net displacement). OFD may in part depend on displacement magnitude, where locations along the rupture with smaller displacements (<2 m) are characterized by a greater percentage of OFD. Furthermore, OFD increases with rupture zone width, especially at the scale of individual rupture strands (hundreds of meters). These findings contribute to a growing understanding of the important role of OFD in accommodating deformation near the surface. Key Points: Comparison of surface displacement from Mw6.4 and Mw7.1 2019 Ridgecrest earthquakes measured in the field and from optical pixel correlationMean treatment of all field measurements account for 41% (Mw6.4) and 65% (Mw7.1) of net displacement documented via optical pixel correlationDifference between field‐based and remotely sensed displacements attributed to off‐fault deformation processes [ABSTRACT FROM AUTHOR]

Focusing on stratified tropospheric delay correction in the small-amplitude coseismic displacement field of small-to-moderate earthquakes (

Traditional coseismic displacement retrieval generally uses real-time kinematic (RTK) and precise point positioning (PPP) services. However, both RTK and real-time PPP need a network link to transmit the corrected data. Although the network link may be interrupted when an earthquake happens, the PPP-B2b service broadcasted by geostationary orbit (GEO) satellites will not be affected. Its service range mainly covers China and the surrounding areas. In this research, the PPP method with PPP-B2b service based on constrained coordinates is proposed and overcomes the limitation of the network link and long convergence time. First, the accuracy of orbits and clock offsets for the PPP-B2b service is evaluated and compared with real-time service (RTS). Then, the simulated experiments are carried out using the PPP method with PPP-B2b service based on constrained coordinates, which tests the accuracy by calculating the coordinate displacement of the measurement station. The results show that the accuracy of PPP-B2b orbits in the radial direction is within 0.1 m. Moreover, regarding the accuracy of clock offsets, the PPP-B2b service is no more than 3.5 cm. This validates the feasibility of replacing RTS products with PPP-B2b. In the 15 min simulated experiments, the root mean square (RMS) of horizontal and vertical directions is maintained within 3 cm.

Surface displacements associated with earthquake-cycle deformation of active faults significantly influence the accuracy of geodetic datum and reference frames, especially for the Taiwan area with high plate convergence and deformation rates. Following the current architecture of the semi-kinematic reference frame in Taiwan, which does not particularly consider the non-linear behavior of postseismic deformation, we explored the methods to implement a non-linear postseismic deformation model using the 2003 Chengkung earthquake as an example. Together with linear interseismic function, we utilized a logarithmic function to approximate the non-linear postseismic decays. For the time series without preseismic observations, we removed the interseismic velocities by spatial interpolation and fitted the resultant time series with the logarithmic function. After estimating postseismic decays for all GPS stations, we conducted two grid models of accumulative displacements for only postseismic deformation and total deformation after the earthquake. The first grid model provides a useful prediction for tracking surface movements, and the latter model provides a straightforward view to access the timing and amount of displacements to correct the semi-kinematic reference frame. The implementation of the grid models can well approximate non-linear postseismic trends for the semi-kinematic reference frame. [ABSTRACT FROM AUTHOR]

We analyzed GPS data to investigate the source parameters of the 2014 North Aegean earthquake (Mw 6.9). We simultaneously inverted strike, dip, rake, average slip, moment, size, and location of the mainshock rupture using coseismic displacements. We also investigated static stress change associated with the mainshock and its influence on aftershock activity. Previous solutions of focal mechanism showed that mainshock has a nearly pure strike-slip nature. Our results also indicate that the mainshock has a right lateral strike-slip mechanism with a substantial extensional component. Average coseismic slips are 48 cm and 25 cm on the horizontal and vertical axis, respectively. Coseismic displacements reach up to 51.35 ± 4.55 mm at ~60 km from the hypocenter (LEMN station). It appears that the mainshock ruptured a fault section approximately 28 km deep and 70 km long and generated a stress drop along the ruptured segment ranging between 3 and 10 bar, with a stress increase of 3 bar at the edges of the rupture. Aftershocks were distributed to a broader area as coseismic stress increase affected a 200-km-long section of the western North Anatolian Fault. [ABSTRACT FROM AUTHOR]

In 2018 the Kilauea volcano erupted and on May 5, an earthquake of M6.9 occurred in Hawaii. Though the methods used by the authors to get the results in the regional reference frame and the methods for NA12 results are different in some way, both results for NA12 are in good agreement. The results in NA12 at GPS continuous observation stations, directly obtained from http://geodesy.unr.edu, were ana⁃ lyzed to show crustal motions in Hawaii. The preseismic crustal movements were dominated by deforma⁃ tion precursory to the earthquake while the influence of the volcanic eruption was secondary. The coseis⁃ mic displacements were the result of the rupture of the earthquake fault. The post seismic displacements around the crater were quite large but localized in a rather small area. No accumulated preseismic vertical displacements were observed near the epicenter. The coseismic horizontal displacements were instant and dramatic displacements in opposite sense to the accumulated preseismic horizontal displacements so they were elastic rebound of the accumulated preseismic horizontal displacements. Therefore, the accumulated preseismic horizontal displacements were precursors to the earthquake. In comparison to other large earthquakes, the media of a quite small area around the epicenter was nearly elastic. The crustal move⁃ ments near the epicenter, imminent to the earthquake were quite significant. They showed the preslip of the earthquake fault or preseismic displacements. This earthquake is a special case that showed the existence of imminent deformation precursory to the earthquake. They are new clues for the future observations and study on the imminent precursors. The M6.9 earthquake in Hawaii was the result of compression of the crust of the island by horizontal motion in NW direction before the earthquake, which led to shear rupture of the earthquake fault that caused the earthquake. This fact is in good agreement with the model of rebound or elastic rebound proposed by the authors, the compression-shear model of rebound or elastic rebound, that is, the model of preseismic compression that leads to shear rupture of the earthquake. [ABSTRACT FROM AUTHOR]

Highlights • Most recent rupture of the eastern segment of the Altyn Tagh fault extended ∼ 83 km with 4.5-m coseismic displacement. • The most recent earthquake on the eastern segment was a M7.3 (2720–2800 a BP) • A huge displacement deficit has accumulated with potential to trigger >M7.8 events. • Eastern segment Holocene seismic activity differs from that on other segments. • Eastern segment Holocene seismic activity tends to be more representative of a variable seismic model. Abstract We performed field investigations to reconstruct the paleoearthquake history of eastern segment of the Altyn Tagh fault, NW China. Investigation at the Saohu spring trench and Shibaocheng west trench sites result in the identification three well-resolved earthquakes, designated as events E 1 , E 2 and E 3 , within the last ∼7000 years. Radiocarbon dates of detrital charcoal provide constraints on the timing of faulting events. The most recent surface-rupturing earthquake, event E 1 dated between 2720 and 2800 years (a) before present (BP), had a rupture length of ∼ 83 km, extending from Hongliuxia to Bagexia, with a coseismic displacement of about 4.5 m. The penultimate event, E 2 , occurred between 4180 and 4970 a BP and may have ruptured from Subei to Bagexia with a coseismic displacement of > 7 m. The third youngest event, E 3 , occurred approximately 6440–7180 a BP and may have ruptured the whole segment from Subei to Kuantan mountain, with a coseismic displacement of >10 m. Holocene earthquake recurrence behavior on the eastern segment of the Altyn Tagh fault conforms to a variable slip earthquake model. Together with previous studies of slip rate, the huge displacement deficit along the eastern segment indicates a high earthquake risk for the surrounding region; the fault has the potential to trigger earthquakes of greater than M7.8, or a period of clustered earthquake activity. The displacement deficit could also indicate that sub-faults in the western Qilian Mountains have absorbed more lateral extrusion of the plateau during the Holocene, which would result in a decreasing fault slip rate and weakening of the eastern extension or outward expansion of the Altyn Tagh fault. [ABSTRACT FROM AUTHOR]

The first regional seismic landslide hazard assessment for Northeastern Mexico is presented. Regional maps predicting the expected areal limits for potential earthquake-induced landslides in terms of coseismic displacements for the 2010 San Pedro earthquake (M 4.0) and two postulated M 5.5 and M 6.5 scenario earthquakes are shown. Permanent displacements were obtained from a global empirical regression based on a critical acceleration ratio (ac/PGA) estimation. Results for the M 4.0 San Pedro event show low cumulative displacements concentrated around the epicentral zone. For this event, occurrence of a few small landslides as disrupted slides and falls were likely. For M 5.5 and M 6.5 scenarios the coseismic displacements depict a high potential for widespread and complex slope failures mainly in the Sierra Madre Oriental hilly areas, although foothills inside the Monterrey Metropolitan Area would be affected. The worst scenario we have postulated is a M 6.5 earthquake during the hurricane season. Hypothetical full-saturated and strong seismic shaking conditions would trigger several rock and soil avalanches as well as other complex landslides. Related damage for this event would be very catastrophic to civil infrastructure and substantial injuries and loss of life are expected mainly in the southwestern portion of the Monterrey Metropolitan Area. Results constitute a useful tool in order to mitigate potential earthquake-induced damage related to regional slope failures. [ABSTRACT FROM AUTHOR]

With the rapid development of the global navigation satellite system (GNSS), high-rate GNSS has been widely used for high-precision GNSS coseismic displacement retrieval. In recent decades, relative positioning (RP) and precise point positioning (PPP) are mainly adopted to retrieve coseismic displacements. However, RP can only obtain relative coseismic displacements with respect to a reference station, which might be subject to quaking during a large seismic event. While PPP needs a long (re)convergence period of tens of minutes. There is no convergence time needed in the variometric approach for displacements analysis standalone engine (VADASE) but the derived displacements are accompanied by a drift. Temporal point positioning (TPP) method adopts temporal-differenced ionosphere-free phase measurements between a reference epoch and the current epoch, and there is almost no drift in the displacement derived from TPP method. Nevertheless, the precise orbit and clock products should be applied in the TPP method. The studies in recent years are almost based on the postprocessing precise orbits and clocks or simulated real-time products. Since 2013, international GNSS service (IGS) has been providing an open-access real-time service (RTS), which consists of orbit, clock and other corrections. In this contribution, we evaluated the performance of real-time coseismic displacement retrieval based on TPP method with IGS RTS correction products. At first, the real-time precise orbit and clock offsets are derived from the RTS correction products. Then, the temporal-differenced ionosphere-free (IF) combinations are formed and adopted as the TPP measurements. By applying real-time precise orbit and clock offsets, the coseismic displacement can be real-timely retrieved based on TPP measurements. To evaluate the accuracy, two experiments including a stationary experiment and an application to an earthquake event were carried out. The former gives an accuracy of 1.8 cm in the horizontal direction and 4.1 cm in the vertical direction during the whole period of 15-min. The latter gives an accuracy of 1.2 cm and 2.4 cm in the horizontal and vertical components, respectively.

Abstract Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from InSAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the M S7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were constructed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault, rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake.

An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coordinates time series, velocity and strain model around the seismic zones from processing of continuous observations from 2010 and 6 times of surveying Global Positioning System (GPS) data since 2009. The results show that, before the earthquake, the eastern segmentation of the Qilian tectonic zone where the Lenglongling Fault located is in strong crustal shortening and compressional strain state with dilatational rates of −15 to −25 ppb. The Lenglongling Fault has a strike-slip rate of 3.1 mm/a and a far-field differential orthogonal rate of 7 mm/a, while differential rate is only 1.2 mm/a near the fault, which reflects its locking feature with strain energy accumulation and high seismic risks. Dynamic evolution of deformation model shows that pre-event dilatational rates around the seismic zones increases from −15 ppb/a to −20 ppb/a with its center moving to the source areas. Time series of N components of G337 station, which is 13.7 km away from the Lenglongling Fault, exhibit a 5 mm/a acceleration anomaly. Time series of base-station QHME (in Menyuan) displays a reverse acceleration from the end of Sep. to Dec., 2016 when it comes to a largest deviation, and the accumulative displacement is more than 4 mm and the value reverse till the earthquake. In our results, coseismic displacement of N, E, U components in QHME site are 3.0 mm, 3.0 mm, −5.4 mm, respectively. If we profile these values onto the Lenglongling Fault, we can achieve a 1.1 mm of strike slip and 4.1 mm updip slip relative to the hanging wall.

the coseismic and the preseismic displacements in the regional reference frame were obtained for the M7.8 earthquake on Nov. 13, 2016 in New Zealand based on time series of coordinates at continuous GPS observation stations, available from http://geodesy.unr.edu, in New Zealand and Australia. horizontal displacement time series vectors at CMBL and KAIK in New Zealand and at USUD and TSKB in Japan are shown. The vector time series show clearly with direct visual effect that the coseismic horizontal displacements were sudden and dramatic, and opposite to the accumulated preseismic horizontal displacements. These represent a rebound or elastic rebound of the accumulated preseismic horizontal displacements. Therefore, the accumulated preseismic horizontal displacements were precursors to the earthquakes. Results produced from the abundant GPS observations are used to discuss the rebound and elastic rebound models. Detailed reanalysis on the results of GPS observations of the M9.0 Tohoku earthquake in Japan shows that one principal strain in the region at and around the epicenter was dominated by compression in the east direction before the earthquake. Moreover, the earthquake and the coseismic displacements were the result of shear rupture at the earthquake faults. This agrees with test of rock failure results, strain analysis, and consistent with earthquake mechanisms. [ABSTRACT FROM AUTHOR]

The paper starts recalling the various stages that lead to the definition of the Early Byzantine Tectonic Paroxysm (EBTP), which was determined mainly from fossil uplifted shorelines of the Eastern Mediterranean between the middle of the 4th century and the middle of the 6th century CE. A comparison of catalogues of earthquakes may show that possibly an important event occurred in 361 CE in the northern Adriatic, i.e. near the beginning of a sequence of clustered earth movements. This event is proposed as the most likely for the coseismic subsidence of a known slightly submerged tidal notch that developed along over 200 km of the Croatian shoreline. [ABSTRACT FROM AUTHOR]

Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from InSAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the M 7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were constructed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault, rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake. [ABSTRACT FROM AUTHOR]

By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China (CMONOC) near the 2013 Lushan Ms7. 0 earthquake, we found a horizontal displacement of 22 mm at a site about 32 km SW of the epicenter and vertical displacements of as much as 12. 4 mm at several sites. The vertical displacements were generally uplift on the west side of the nearby Longmenshan fault zone and subsidence on the east side. We also found coseismic ionospheric disturbances about 0. 5 to 0. 9 TECU in amplitude that lasted for about one hour.

It is generally recognized that permanent displacements estimated by the double integration of acceleration records need a suitable baseline correction. Current baseline correction methods have been validated by comparing the displacements with those from the Global Positioning System (GPS) records nearby, but GPS stations that are sufficiently close to a strong-motion station are scarce. Because the Tohoku-Oki earthquake produced geodetic displacements in a wide area and because dense strong-motion and GPS networks are available in Japan, we interpolated the displacements calculated from GPS records to estimate the permanent displacements at 508 strong-motion stations. The estimated results were used to evaluate uncertainties in permanent displacements obtained using two baseline correction methods, and results were found to be reliable only for KiK-net's borehole acceleration records. A new joint parameter search method for the surface and borehole records was further proposed, and reliable results were obtained for KiK-net's surface records. [ABSTRACT FROM AUTHOR]

We propose a coseismic slip distribution inversion method based on variance component estimation (VCE), this method not only determines the weight of different data sets but also can get the smoothing factor value. To illustrate and validate this inversion method, we conducted inversions on synthetic data sets. Based on the Bayesian framework and according to the posterior probability density distribution of the unknown parameters, the proposed solution is comparted to one of the linear-non-linear inversion solutions to further demonstrate the use of the proposed method. We conduct inversions on the 2003 Bam earthquake with the proposed method and linear-non-linear inversion method, the spatial cross correlation of the resulting slip distribution was about 0.999, the depth of the max slip of the both were 3.04 m and the depth had little difference, the former was 4.50 km, the latter was 4.47 km. The mean slip in the former was 0.714 m, the latter was 0.718 m. But the inversion time of the former was 227 s, and only about 1/8 000 of the later (reaching 1.5×106 s, about 17 d).These results show that the VCE method is effective and faster than the linear-non-linear inversion method. [ABSTRACT FROM AUTHOR]