Processed strong-motion data for the El Salvador earthquake of June 19, 1982

In this paper we compare two time-domain inversion methods that have been widely applied to the problem of modeling earthquake rupture using strong-motion seismograms. In the multi-window method, each point on the fault is allowed to rupture multiple times. This allows flexibility in the rupture time and hence the rupture velocity. Variations in the slip-velocity function are accommodated by variations in the slip amplitude in each time-window. The single-window method assumes that each point on the fault ruptures only once, when the rupture front passes. Variations in slip amplitude are allowed and variations in rupture velocity are accommodated by allowing the rupture time to vary. Because the multi-window method allows greater flexibility, it has the potential to describe a wider range of faulting behavior; however, with this increased flexibility comes an increase in the degrees of freedom and the solutions are comparatively less stable. We demonstrate this effect using synthetic data for a test model of the Mw 7.3 1992 Landers, California earthquake, and then apply both inversion methods to the actual recordings. The two approaches yield similar fits to the strong-motion data with different seismic moments indicating that the moment is not well constrained by strong-motion data alone. The slip amplitude distribution is similar using either approach, but important differences exist in the rupture propagation models. The single-window method does a better job of recovering the true seismic moment and the average rupture velocity. The multi-window method is preferable when rise time is strongly variable, but tends to overestimate the seismic moment. Both methods work well when the rise time is constant or short compared to the periods modeled. Neither approach can recover the temporal details of rupture propagation unless the distribution of slip amplitude is constrained by independent data.

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The INGV real time strong motion data sharing during the 2016 Amatrice (central Italy) seismic sequence

Annals of Geophysics ◽

10.4401/ag-7193 ◽

2016 ◽

Vol 59 ◽

Author(s):

Marco Massa ◽

Ezio D'Alema ◽

Chiara Mascandola ◽

Sara Lovati ◽

Davide Scafidi ◽

...

Keyword(s):

Real Time ◽

Data Sharing ◽

Strong Motion ◽

Main Task ◽

Seismic Sequence ◽

Web Portal ◽

Epicentral Area ◽

Strong Motion Data ◽

Motion Data ◽

The Web

ISMD is the real time INGV Strong Motion database. During the recent August-September 2016 Amatrice, Mw 6.0, seismic sequence, ISMD represented the main tool for the INGV real time strong motion data sharing. Starting from August 24th, the main task of the web portal was to archive, process and distribute the strong-motion waveforms recorded by the permanent and temporary INGV accelerometric stations, in the case of earthquakes with magnitude ≥ 3.0, occurring in the Amatrice area and surroundings. At present (i.e. September 30th, 2016), ISMD provides more than 21.000 strong motion waveforms freely available to all users. In particular, about 2.200 strong motion waveforms were recorded by the temporary network installed for emergency in the epicentral area by SISMIKO and EMERSITO working groups. Moreover, for each permanent and temporary recording site, the web portal provide a complete description of the necessary information to properly use the strong motion data.

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