Home »

 
 

HERE

 

High-resolution seismicity locations and repeating events.

People:

Luisa Valoroso – luisa.valoroso@ingv.it

Lauro Chiaraluce – lauro.chiaraluce@ingv.it

Raffaele Di Stefano – raffaele.distefano@ingv.it

The characterization of the geometry, kinematics and rheology of fault zones by seismological data depends on our capability of recording and accurately locate the larger number of low-magnitude seismic events. To this aim, we combine data coming from seismic stations located at surface with (shallow) boreholes seismometers of the TABOO network. We analyse these data by means of an accurate automatic picking procedure for P- and S-waves [a], together with cross-correlation and double-difference location methods [b]. The combined use of these procedures results in earthquake relative location uncertainties in the range of a few meters to tens of meters, comparable/lower than the spatial dimension of the earthquakes themselves.

We will also investigate the mechanical behaviour of the ATF by focusing on the occurrence of clusters of repeating earthquakes (i.e., events that repeatedly rupture the same fault patch with nearly identical waveforms, locations, and magnitudes). In this framework, accurate location of repeaters on the fault plane can be used to discriminate between patches of the fault that undergo unstable sliding from those regions of stable sliding creeping [c], while the spatiotemporal evolution of repeating events can be used to monitor changes in the velocity structure of fault zones [d].

References

  1. Aldersons, F., R. Di Stefano, L. Chiaraluce, D. Piccinini, and L. Valoroso (2009), Automatic detection, and P and S wave picking algorithm: An application to the 2009 L’Aquila (central Italy) earthquake sequence, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract U23B-0045.

  1. Waldhauser, F., and D. P. Schaff (2008), Large-scale relocation of two decades of Northern California seismicity using cross-correlation and double-difference methods, J. Geophys. Res., 113, 979 B08311, doi:10.1029/2007JB005479.

  1. Rubin, A. M., Gillard, D., and Got, J.L., 1999. Streaks of microearthquakes along creeping faults. Nature, 400, 635-641.

  1. Schaff, D. P., and G. C. Beroza (2004), Coseismic and postseismic velocity changes measured by repeating earthquakes, J. Geophys. Res., 109, B10302, doi:10.1029/2004JB003011.