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[1] Large-scale crustal deformation in the Levant is mainly related to the DST and the CFS. The former is an active left lateral transform, bounding the Arabian plate and the Sinai sub-plate, and the latter branches out of the former and separates the Sinai sub-plate into two tectonic domains. In this study we obtain the velocities of 33 permanent GPS stations and 145 survey stations that were surveyed in three campaigns between 1996 and 2008. We use a simple 1-D elastic dislocation model to infer the slip rate and locking depth along various segments of the DST. We infer a 3.1-4.5 mm/yr slip rate and a 7.8-16.5 km locking depth along the DST north of the CFS, and a slip rate of 4.6-5.9 mm/yr and locking depth of 11.8-24 km along the Jericho Valley, south of the CFS. Further south, along the Arava Valley we obtain a slip rate of 4.7-5.4 mm/yr and a locking depth of 12.1-23 km. We identify an oblique motion along the Carmel Fault with $0.7 mm/yr left-lateral and $0.6 mm/yr extension rates, resulting in N-S extension across the Carmel Fault. This result, together with the decrease in DST slip velocity from the Jericho Valley to the segment north of the CFS, confirms previous suggestions, according to which part of the slip between Arabia and Sinai is being transferred from the DST to the CFS.

[1] We explore the use of real-time high-rate GPS displacement data for earthquake early warning using 1 Hz displacement waveforms from the April 4, 2010, M w 7.2 El Mayor-Cucapah earthquake. We compare these data to those provided by the broadband velocity and accelerometer instrumentation of the Southern California Seismic Network. The unique information provided by the GPS-based displacement timeseries is the permanent/static displacement. Using a simple algorithm that can be applied in real-time, we extract the static offset shortly after the S-wave arrival, around the time of the observed peak shaking at the same site, and before shaking at more distant locations. These data can be used, as they become available, to provide a robust estimate of the earthquake magnitude, which ranges from 6.8 to 7.0 in this case. We therefore conclude that real-time highrate GPS can provide a useful and independent assessment of earthquake magnitude for the purpose of earthquake early warning and real-time earthquake information systems in general including tsunami warning systems. Citation: Allen, R. M., and A. Ziv (2011), Application of real-time GPS to earthquake early warning, Geophys.

between these results and those obtained for synthetic catalogs, in which the timing or focal mechanisms of the earthquakes were randomized, shows that this degree of triggering is very unlikely to be found in a random catalog. Thus we conclude that no lower threshold for earthquake triggering in central California has been found. We show that the temporal distribution of stress changes that discourage failure is consistent with the theoretical prediction that the time delay increases with the magnitude of the stress change.

[1] Dieterich [1994] modeled the response to a stress step of a population of faults governed by rate-and state-dependent friction. This model assumes that aftershocks nucleate over areas on the fault that at the time of the main shock are already accelerating toward failure and disregards the effect of interactions among aftershocks. The main objective of this study is to examine consequences of relaxing these underlying assumptions. Aftershock activity is simulated using an inherently discrete earthquake fault model, with a fault surface governed by an approximate constitutive friction law similar to the one used by Dieterich. We find that the governing equations in nondimensional form are a function of three main parameters and explore the effect of these parameters on the simulated catalogs. We derive a simple expression for the time-dependent seismicity response to a stress step that approximates the effect of multiple interactions among aftershocks as a time-dependent stressing rate. Close match is found between the simulated seismicity response to a stress step and that predicted analytically. However, the numerical simulations show that the effect of the main shock is not only to raise the local seismicity rate but also to systematically modify the earthquake size distribution. As a result, the actual seismicity rate change early during the aftershock sequence may be higher than that predicted, whereas seismicity rate late in the sequence may be lower than that predicted. Such a modification of the earthquake size distribution can explain observations of lower b values immediately following a stress step.INDEX TERMS: 7230 Seismology: Seismicity and seismotectonics; 7209 Seismology: Earthquake dynamics and mechanics; 7223 Seismology: Seismic hazard assessment and prediction; KEYWORDS: aftershock model, earthquakes simulation, rate-and state-dependent friction, spatiotemporal analyses Citation: Ziv, A., and A. M. Rubin, Implications of rate-and-state friction for properties of aftershock sequence: Quasi-static inherently discrete simulations,