Preliminary Report from GEER

The Preliminary Report on the Seismological and Geotechnical Aspects of the April 6 2009 L’Aquila Earthquake in Central Italy can be read on GEER’s website (click title).

GEER findings – dams

We have visited the three dams at Campotosto Lake, which is a large reservoir north of L’Aquila. Performance was good. At least one of the dams is instrumented but we have not been able to secure the data. Read more

GEER findings – damage patterns

We examined damage patterns at two scales  – damage within L’Aquila and regional damage distribution based on impact in small villages (figure below). The figure below shows our track logs and call out places we visited as of Wednesday April 15. In most cases we have approximate damage statistics for those villages. Read more

GEER findings – source description (very preliminary)

The faulting associated with this earthquake is complex and is not yet well understood. We hope to have a working hypothesis for the faulting mechanism by the time we publish our preliminary report in early May. The relevant data sources include the aftershock pattern and its variation with time, moment tensor solutions of the mainshock and aftershocks, and SAR data. Read more

GEER findings – ground motions

We have not looked at individual records yet, but we have the motions for the mainshock, largest aftershock, and triggered event from a DPC website. The mainshock data have been forwarded to PEER and CESMD for processing. We have 56 mainshock recordings, including 4 in the immediate vicinity of L’Aquila. Three of those are west of the city in a sparsely developed valley (however, this is near the hospital). The fourth is near the historic center of L’Aquila. The center sits on a Pleistocene terrace. There is a swale east of the center, and the instrument is above a pedestrian tunnel portal on the edge slope of the Pleistocene terrace (nearby structure is a car park). We were not able to walk up to the instrument because access to the car park is  denied.  This instrument recorded about 0.35 g. The instruments W of L’Aquila recorded 0.5-0.7 g.

GEER findings – ground failure

We did not found evidence for surface fault rupture. Scott Kieffer, Teddy Button, and students looked in the area of the Pettino and Paganica faults. Both faults are very well expressed at the surface, but we did not find evidence of displacement from this earthquake. However, recent reports from others indicate some ground failure in vicinity of Paganica fault, and some geologists are going into the field to look more carefully at this. Therefore, it is too early to conclude that there was no surface rupture. Read more

GEER team – overview of activities

The GEER team deployed on April 10 and worked through April 18. Additional observations will continue to come in as additional teams go into the field. We have made every effort to provide our findings to the leadership of those teams to optimize their efficiency. Read more

GEER Deployment

Scott Kieffer arrive last night and is in field today. Remaining team members (Giovanna Biscontin, Robert Kayen, and Jonathan Stewart) to arrive Sunday and will begin work immediately with Giuseppe Scasserra. Other Italian team members will join us on Tuesday.