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Measurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the subduction interface and may also show up in the fore‐arc morphology. To investigate this hypothesis, we compiled information on the extent of earthquake ruptures for the last 500 years and uplift rates derived from dated marine terraces along the South American coastline from central Peru to southern Chile. We additionally calculated a new interseismic coupling model for that same area based on a compilation of GPS data. We show that the coastline geometry, characterized by the distance between the coast and the trench; the latitudinal variations of long‐term uplift rates; and the spatial pattern of interseismic coupling are correlated. Zones of faster and long‐term permanent coastal uplift, evidenced by uplifted marine terraces, coincide with peninsulas and also with areas of creep on the megathrust where slip is mostly aseismic and tend to arrest seismic ruptures. We conclude that spatial variations of frictional properties along the megathrust dictate the tectono‐geomorphological evolution of the coastal zone and the extent of seismic ruptures along strike.

We determined the overall efficiency for 10 Be of the high-intensity LLNL modified Middleton cesium sputter source in combination with the CAMS FN mass 1 spectrometer. BeO -ionization efficiency is >3%. Charge exchange efficiency including transmission through the tandem for 7.5MeV Be +3 is ~34%, resulting in a total system efficiency of just over 1%. At this efficiency and with very low backgrounds, we estimate our detection limit to be ~1000 10 Be atoms. Cathodes prepared with only ~80 micrograms of 9 Be show only an ~33% reduction in 9 Be beam current compared to a sample with ~200 micrograms. These same samples, prepared from 07KNSTD1032 standard material, contained 1 x 10 7 and 5 x 10 6 10 Be atoms and exhibited similar ionization and total system efficiency. These results demonstrate the feasibility of pursuing applications that require precise measurement of samples with low 10 Be concentrations and/or small sample size.

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