Very high rate (10 Hz) GPS seismology for moderate-magnitude earthquakes: The case of the<i>M</i>_<i>w</i>6.3 L'Aquila (central Italy) event

Abstract

[1] The 6 April 2009 Mw 6.3 L'Aquila destructive earthquake was successfully recorded by closely spaced 10 Hz and 1 Hz recording GPS receivers and strong motion accelerometers located above or close to the 50° dipping activated fault. We retrieved both static and dynamic displacements from very high rate GPS (VHRGPS) recordings by using Precise Point Positioning kinematic analysis. We compared the GPS positions' time series with the closest displacement time series obtained by doubly integrating strong motion data, first, to assess the GPS capability to detect the first seismic arrivals (P waves) and, second, to evaluate the accelerometers' capability to detect coseismic offsets up to ∼45 s after the earthquake occurrence. By comparing seismic and VHRGPS frequency contents, we inferred that GPS sampling rates greater than 2.5 Hz (i.e., 5 or 10 Hz) are required in the near field of moderate-magnitude events to provide “alias-free” solutions of coseismic dynamic displacements. Finally, we assessed the consistency of the dynamic VHRGPS results as a constraint on the kinematic rupture history of the main shock. These results suggested that the high-rate sampling GPS sites in the near field can be as useful as strong motion stations for earthquake source studies.