Land subsidence over oilfields in the Yellow River Delta

Subsidence in river deltas is a complex process that has both natural and human causes. Increasing human activities like aquaculture and petroleum extraction are affecting the Yellow River delta, and one consequence is subsidence. The purpose of this study is to measure the surface displacements in the Yellow River delta region and to investigate the corresponding subsidence source. In this paper, the Stanford Method for Persistent Scatterers (StaMPS) package was employed to process Envisat ASAR images collected between 2007 and 2010. Consistent results between two descending tracks show subsidence with a mean rate up to 30 mm/yr in the radar line of sight direction in Gudao Town (oilfield), Gudong oilfield and Xianhe Town of the delta, each of which is within the delta, and also show that subsidence is not uniform across the delta. Field investigation shows a connection between areas of non-uniform subsidence and of petroleum extraction. In a 9 km2 area of the Gudao Oilfield, a poroelastic disk reservoir model is used to model the InSAR derived displacements. In general, good fits between InSAR observations and modeled displacements are seen. The subsidence observed in the vicinity of the oilfield is thus suggested to be caused by fluid extraction

Satellite SAR Interferometry for Earth’s Crust Deformation Monitoring and Geological Phenomena Analysis

Synthetic aperture radar interferometry (InSAR) and the related processing techniques provide a unique tool for the quantitative measurement of the Earth’s surface deformation associated with certain geophysical processes (such as volcanic eruptions, landslides and earthquakes), thus making possible long-term monitoring of surface deformation and analysis of relevant geodynamic phenomena. This chapter provides an application-oriented perspective on the spaceborne InSAR technology with emphasis on subsequent geophysical investigations. First, the fundamentals of radar interferometry and differential interferometry, as well as error sources, are briefly introduced. Emphasis is then placed on the realistic simulation of the underlying geophysics processes, thus offering an unfolded perspective on both analytical and numerical approaches for modeling deformation sources. Finally, various experimental investigations conducted by acquiring SAR multitemporal observations on areas subject to deformation processes of particular geological interest are presented and discussed

Slip distribution of the 2017 M(w)6.6 Bodrum-Kos earthquake: resolving the ambiguity of fault geometry

SUMMARY The 2017 July 20, Mw6.6 Bodrum–Kos earthquake occurred in the Gulf of Gökova in the SE Aegean, a region characterized by N–S extension in the backarc of the easternmost Hellenic Trench. The dip direction of the fault that ruptured during the earthquake has been a matter of controversy where both north- and south-dipping fault planes were used to model the coseismic slip in previous studies. Here, we use seismic (seismicity, main shock modelling, aftershock relocations and aftershock mechanisms using regional body and surface waves), geodetic (GPS, InSAR) and structural observations to estimate the location, and the dip direction of the fault that ruptured during the 2017 earthquake, and the relationship of this event to regional tectonics. We consider both dip directions and systematically search for the best-fitting locations for the north- and south-dipping fault planes. Comparing the best-fitting planes for both dip directions in terms of their misfit to the geodetic data, proximity to the hypocenter location and Coulomb stress changes at the aftershock locations, we conclude that the 2017 earthquake ruptured a north-dipping fault. We find that the earthquake occurred on a 20–25 km long, ∼E–W striking, 40° north-dipping, pure normal fault with slip primarily confined between 3 and 15 km depth, and the largest slip exceeding 2 m between depths of 4 and 10 km. The coseismic fault, not mapped previously, projects to the surface within the western Gulf, and partly serves both to widen the Gulf and separate Kos Island from the Bodrum Peninsula of SW Anatolia. The coseismic fault may be an extension of a mapped, north-dipping normal fault along the south side of the Gulf of Gökova. While all of the larger aftershocks are consistent with N–S extension, their spatially dispersed pattern attests to the high degree of crustal fracturing within the basin, due to rapid trenchward extension and anticlockwise rotation within the southeastern Aegean

Depth-Varying Friction on a Ramp-Flat Fault Illuminated by ∼3-Year InSAR Observations Following the 2017 Mw 7.3 Sarpol-e Zahab Earthquake

We use interferometric synthetic aperture radar observations to investigate the fault geometry and afterslip evolution within 3 years after a mainshock. The postseismic observations favor a ramp-flat structure in which the flat angle should be lower than 10°. The postseismic deformation is dominated by afterslip, while the viscoelastic response is negligible. A multisegment, stress-driven afterslip model (hereafter called the SA-2 model) with depth-varying frictional properties better explains the spatiotemporal evolution of the postseismic deformation than a two-segment, stress-driven afterslip model (hereafter called the SA-1 model). Although the SA-2 model does not improve the misfit significantly, this multisegment fault with depth-varying friction is more physically plausible given the depth-varying mechanical stratigraphy in the region. Compared to the kinematic afterslip model, the mechanical afterslip models with friction variation tend to underestimate early postseismic deformation to the west, which may indicate more complex fault friction than we expected. Both the kinematic and stress-driven models can resolve downdip afterslip, although it could be affected by data noise and model resolution. The transition depth of the sedimentary cover basement interface inferred by afterslip models is ∼12 km in the seismogenic zone, which coincides with the regional stratigraphic profile. Because the coseismic rupture propagated along a basement-involved fault while the postseismic slip may activate the frontal structures and/or shallower detachments in the sedimentary cover, the 2017 Sarpol-e Zahab earthquake may have acted as a typical event that contributed to both thick- and thin-skinned shortening of the Zagros in both seismic and aseismic ways

Analysis and interpretation of volcano deformation in Alaska: Studies from Okmok and Mt. Veniaminof volcanoes

Thesis (Ph.D.) University of Alaska Fairbanks, 2008Four studies focus on the deformation at Okmok Volcano, the Alaska Peninsula and Mt. Veniaminof. The main focus of the thesis is the volcano deformation at Okmok Volcano and Mt. Veniaminof, but also includes an investigation of the tectonic related compression of the Alaska Peninsula. The complete data set of GPS observations at Okmok Volcano are investigated with the Unscented Kalman Filter time series analysis method. The technique is shown to be useful for inverting geodetic data for time dependent non-linear model parameters. The GPS record at Okmok from 2000 to mid 2007 shows distinct inflation pulses which have several months duration. The inflation is interpreted as magma accumulation in a shallow reservoir under the caldera center and approximately 2.5km below sea level. The location determined for the magma reservoir agrees with estimates determined by other geodetic techniques. Smaller deflation signals in the Okmok record appear following the inflation pulses. A degassing model is proposed to explain the deflation. Petrologic observations from lava erupted in 1997 provide an estimate for the volatile content of the magma. The solution model VolatileCalc is used to determine the amount of volatiles in the gas phase. Degassing can explain the deflation, but only under certain circumstances. The magma chamber must have a radius between ~1and 2km and the intruding magma must have less than approximately 500ppm CO2. At Mt. Veniaminof the deformation signal is dominated by compression caused by the convergence of the Pacific and North American Plates. A subduction model is created to account for the site velocities. A network of GPS benchmarks along the Alaska Peninsula is used to infer the amount of coupling along the mega-thrust. A transition from high to low coupling near the Shumagin Islands has important implications for the seismogenic potential of this section of the fault. The Shumagin segment likely ruptures in more frequent smaller magnitude quakes. The tectonic study provides a useful backdrop to examine the volcano deformation at Mt. Veniaminof. After being corrected for tectonic motion the sites velocities indicate inflation at the volcano. The deformation is interpreted as pressurization occurring beneath the volcano associated with eruptive activity in 2005

A Method for Selecting SAR Interferometric Pairs Based on Coherence Spectral Clustering

To achieve accurate interferometric synthetic aperture radar (SAR) phase estimation, it is essential to select appropriate high-coherence interferometric pairs from massive SAR single-look complex (SLC) image data. The selection should include as many high-coherence interferometric pairs as possible while avoiding low-coherence pairs. By combining coherence and spectral clustering, a novel selection method for SAR interferometric pairs is proposed in this article. The proposed method can be adopted to classify SAR SLC images into different clusters, where the total coherence of interferometric pairs in the same cluster is maximized while that among different clusters is minimized. This is implemented by averaging the coherence matrices of representative pixels to construct an adjacency matrix and performing eigenvalue decomposition for estimating the number of clusters. The effectiveness of the proposed method is demonstrated using 33 TerraSAR-X and 38 dual-polarization Sentinel-1A data samples, yielding improved topography and deformation monitoring results

Coseismic Deformation Detection and Quantification for Great Earthquakes Using Spaceborne Gravimetry

This Ohio State University Geodetic Science Report was prepared for, in part, and submitted to the Graduate School of the Ohio State University as a Dissertation in partial fulfillment of the requirements of the Doctor of Philosophy (PhD) degree.This research is conducted under the supervision of Professor C.K. Shum, Division of Geodetic Science, School of Earth Sciences, The Ohio State University. The research results documented in this report resulted in a PhD Dissertation by Lei Wang (2012), Division of Geodetic Science, School of Earth Sciences, The Ohio State University. This research is partially funded by grants from NASA’s Interdisciplinary Science Program (NNG04GN19G), NASA’s Ocean Surface Topography Mission (OSTM) and Physical Oceanography Program (JPL1283230), the Air Force Materiel Command (FA8718-07-C-0021), and NSF’s Division of Earth Sciences (EAR-1013333). We would like to acknowledge Professor Frederik J. Simons, Department of Geosciences, Princeton University, for his hosting of Dr. Lei Wang for the summer visits.Because of Earth’s elasticity and its viscoelasticity, earthquakes induce mass redistributions in the crust and upper mantle, and consequently change Earth’s external gravitational field. Data from Gravity Recovery And Climate Experiment (GRACE) spaceborne gravimetry mission is able to detect the permanent gravitational and its gradient changes caused by great earthquakes, and provides an independent and thus valuable data type for earthquake studies. This study uses a spatiospectral localization analysis employing the Slepian basis functions and shows that the method is novel and efficient to represent and analyze regional signals, and particularly suitable for extracting coseismic deformation signals from GRACE. For the first time, this study uses the Monte Carlo optimization method (Simulated Annealing) for geophysical inversion to quantify earthquake faulting parameters using GRACE detected gravitational changes. GRACE monthly gravity field solutions have been analyzed for recent great earthquakes. For the 2004 Mw 9.2 Sumatra-Andaman and 2005 Nias earthquakes (Mw 8.6), it is shown for the first time that refined deformation signals are detectable by processing the GRACE data in terms of the full gravitational gradient tensor. The GRACE-inferred gravitational gradients agree well with coseismic model predictions. Due to the characteristics of gradient measurements, which have enhanced high-frequency contents, the GRACE observations provide a more clear delineation of the fault lines, locate significant slips, and better define the extent of the coseismic deformation; For the 2010 Mw 8.8 Maule (Chile) earthquake and the 2011 Mw 9.0 Tohoku-Oki earthquake, by inverting the GRACE detected gravity change signals, it is demonstrated that, complimentary to classic teleseismic records and geodetic measurements, the coseismic gravitational change observed by spaceborne gravimetry can be used to quantify large scale deformations induced by great earthquakes

Coseismic Deformation Detection and Quantification for Great Earthquakes Using Spaceborne Gravimetry

This Ohio State University Geodetic Science Report was prepared for, in part, and submitted to the Graduate School of the Ohio State University as a Dissertation in partial fulfillment of the requirements of the Doctor of Philosophy (PhD) degree.This research is conducted under the supervision of Professor C.K. Shum, Division of Geodetic Science, School of Earth Sciences, The Ohio State University. The research results documented in this report resulted in a PhD Dissertation by Lei Wang (2012), Division of Geodetic Science, School of Earth Sciences, The Ohio State University. This research is partially funded by grants from NASA’s Interdisciplinary Science Program (NNG04GN19G), NASA’s Ocean Surface Topography Mission (OSTM) and Physical Oceanography Program (JPL1283230), the Air Force Materiel Command (FA8718-07-C-0021), and NSF’s Division of Earth Sciences (EAR-1013333). We would like to acknowledge Professor Frederik J. Simons, Department of Geosciences, Princeton University, for his hosting of Dr. Lei Wang for the summer visits.Because of Earth’s elasticity and its viscoelasticity, earthquakes induce mass redistributions in the crust and upper mantle, and consequently change Earth’s external gravitational field. Data from Gravity Recovery And Climate Experiment (GRACE) spaceborne gravimetry mission is able to detect the permanent gravitational and its gradient changes caused by great earthquakes, and provides an independent and thus valuable data type for earthquake studies. This study uses a spatiospectral localization analysis employing the Slepian basis functions and shows that the method is novel and efficient to represent and analyze regional signals, and particularly suitable for extracting coseismic deformation signals from GRACE. For the first time, this study uses the Monte Carlo optimization method (Simulated Annealing) for geophysical inversion to quantify earthquake faulting parameters using GRACE detected gravitational changes. GRACE monthly gravity field solutions have been analyzed for recent great earthquakes. For the 2004 Mw 9.2 Sumatra-Andaman and 2005 Nias earthquakes (Mw 8.6), it is shown for the first time that refined deformation signals are detectable by processing the GRACE data in terms of the full gravitational gradient tensor. The GRACE-inferred gravitational gradients agree well with coseismic model predictions. Due to the characteristics of gradient measurements, which have enhanced high-frequency contents, the GRACE observations provide a more clear delineation of the fault lines, locate significant slips, and better define the extent of the coseismic deformation; For the 2010 Mw 8.8 Maule (Chile) earthquake and the 2011 Mw 9.0 Tohoku-Oki earthquake, by inverting the GRACE detected gravity change signals, it is demonstrated that, complimentary to classic teleseismic records and geodetic measurements, the coseismic gravitational change observed by spaceborne gravimetry can be used to quantify large scale deformations induced by great earthquakes