2010 Haiti Earthquake: Afterschock Study from Temporary off Shore and Land Network

One month after the large earthquake which destroyed Port au Prince on 12th of January, we deployed a seismological network of 21 Ocean Bottom Seismometers (OBS) and 4 land stations. 15 OBS instruments were recovered 3 weeks later. We present the analysis of these 3 weeks of seismological records to characterize the aftershocks sequence in order to enlighten the complexity of the main event rupture. We first explore velocity models based on the existing marine profiles and arrival times of a set of well recorded events. It allows us to take into account the low velocity layer below the OBS stations. Aftershocks distribution located with the best model shows that almost all the activity is located on the north of the fault segment activated during the mainshock and is organized into three swarms. The first one is located below Leogane, the second one below the shore in front of Petit Gonave, the third one more on the west and clearly off shore. Those clusters are clearly associated with the main slip patches immaged by the rupture tomogaphy. The depth of the events are well constrained and the distribution shows a large pick between 8 and 12 km. Focal solutions show mainly strike-slip and compression as already noticed for the main shock and the main aftershocks. The location of the 3 events given in the NEIC catalogue during the campaign period presents a systematic shift of about 10km to the NE. If such a shift is apply to the whole data set provided in this catalogue, the aftershocks distribution is in good agreeement with the one we provide and helps to better described the activity just after the main event.