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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.

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]

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.

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.

The 1997 September-October Umbria-Marche sequence has been extensively studied in the past by analyzing coseismic displacement data (GPS, leveling, SAR). Here we focus on synthetic data representative of the main event of the 1997 Umbria-Marche sequence and investigate the effects of a crustal layering proper to the Colfiorito area on surface displacements and inferred source features when inverting coseismic geodetic data without taking into account layering. We compare bootstrapping and NA-Bayes as tools for parameter uncertainty assessment and show how the Akaike Information Criterion can be used to select the model which is most likely to be correct. Since SAR images offer the most complete coverage of the study area, we use synthetic line-ofsight displacement data.