Estimating Slip Distribution for the Izmit Mainshock from Coseismic GPS, ERS-1, RADARSAT, and SPOT Measurements

Abstract

We use four geodetic satellite systems (Global Positioning System [GPS], European Remote Sensing [ERS], RADARSAT, and Satellite Pour l'Observation de la Terre [SPOT]) to measure the permanent deformation field produced by the İzmit earthquake of 17 August 1999. We emphasize measurements from interferometric analysis of synthetic aperture radar (SAR) images acquired by ERS and RADARSAT and their geodetic uncertainties. The primary seismological use of these data is to determine earthquake source parameters, such as the distribution of slip and the fault geometry. After accounting for one month's postseismic deformation, tropospheric delay, and orbital gradients, we use these data to estimate the distribution of slip at the time of the İzmit mainshock. The different data sets resolve different aspects of the distribution of slip at depth. Although these estimates agree to first order with those derived from surface faulting, teleseismic recordings, and strong motion, careful comparison reveals differences of 40% in seismic moment. We assume smooth parameterization for the fault geometry and a standard elastic dislocation model. The root mean square residual scatter is 25 mm and 11 mm for the ERS and RADARSAT range changes, respectively. Our estimate of the moment from a joint inversion of the four geodetic data sets is M 0 ‫ס‬ 1.84 ‫ן‬ 10 20 N m, a moment magnitude of M w 7.50. These values are lower than other estimates using more realistic layered earth models. Given the differences between the various models, we conclude that the real errors in the estimated slip distributions are at the level of 1 m. The prudent geophysical conclusion is that coseismic slip during the İzmit earthquake tapers gradually from approximately 2 m under the Hersek delta to 1 m at a point 10 km west of it. We infer that the Yalova segment west of the Hersek delta may remain capable of significant slip in a future earthquake.

Application of Space-borne Radar Interferometry on Crustal Deformations in Taiwan: A Perspective from the Nature of Events

“…The simulation of an unwrapped interferogram from GPS data can be applied to control possible orbit error in interferometric results (e.g., Hudnut et al 1994;Burgmann et al 2002;Delouis et al 2002;Donnellan et al 2002;Feigl et al 2002). The campaign-surveyed GPS data (data after Yu et al 2001) used in this study were collected from several campaigns mainly conducted by (1) the Central Geological Survey, Ministry of Economic Affairs, (2) the Satellite Survey Division and Land Survey Bureau, Ministry of Interior, and (3) the Institute of Earth Sciences, Academia Sinica.…”

Three-dimensional deformation caused by the Bam, Iran, earthquake and the origin of shallow slip deficit

“…Over the last decade, new information about the near-field deformation due to several large shallow earthquakes was obtained with the help of the space-borne Synthetic Aperture Radar (SAR) measurements [1][2][3] . Interpretations of the spatially continuous SAR data from the best documented seismic events including the M w 7.3 Landers 4 , the M w 7.6 Izmit 5,6 , and the M w 7.1 Hector Mine 3,7,8 earthquakes all reveal the maximum seismic moment release in the middle of the seismogenic layer (the average depth of 4-6 km). While a gradual decay in the coseismic slip at the bottom of the seismogenic layer is likely compensated by postseismic and interseismic strain accumulation, and is reasonably well understood 9-11 , the apparent discrepancy between slip in the middle and shallow parts of the seismogenic layer remains enigmatic.…”

Triangular dislocation: an analytical, artefact-free solution

“…The position and geometry of these sources, as well as the slip or the forces acting on them, are typically regarded as the source parameters. The source parameters, in other words, the outputs of the implemented modelling, are relevant to earthquake aftershock studies, the assessment of volcanic eruption precursors, tsunami modelling and many other applications (Feigl et al 2002).…”

“…The position and geometry of these sources, as well as the slip or the forces acting on them, are typically regarded as the source parameters. The source parameters, in other words, the outputs of the implemented modelling, are relevant to earthquake aftershock studies, the assessment of volcanic eruption precursors, tsunami modelling and many other applications (Feigl et al 2002).The majority of methods that are applied for crustal deformation modelling are based on the theory of elasticity in general and the concept of dislocations in particular (Segall 2010). Elastic dislocation theory concerns the state of deformations in a strained solid body that is subject to the action of a dislocation embedded inside it (Love 1944).…”