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

Main Shock Time Histories from station AQV (provided by M.Celebi, USGS)

Largest peak accelerations of the main shock from station AQV  and their amplitude spectra :  Read more

Local report on new faults

The attached website reports pictures of new faults in the area:

It’s published in the local newspaper “Il Centro”

http://ilcentro.gelocal.it/multimedia/home/5466682/4

Silvio Calvi

GEER Update Apr 12 2009

Ground motions: uncorrected mainshock data obtained (56 triaxial recordings) & will be forwarded Brian Chiou shortly for processing at PEER.

Fault: No surface rupture found, but likely scarp of normal fault identified. Aftershock pattern suggests two-segment rupture in mainshock. Possible triggered second event several days after mainshock on separate fault with its own aftershock distribution.

Tentative evidence of site effects identified in LAquila, mapping forthcoming.

Ground failure around lake, mapping forthcoming.

Some rockfalls that damaged structures.

Basic Earth Science Information

USGS Moment Tensor
Shakemap
Italian seismic sources