Crowdsourcing as a seismic damage assessment tool: a case study on 2011 Christchurch earthquakes.

Crowdsourcing is the act of taking a job traditionally performed by a designated agent (usually an employee) and outsourcing it to an undefined, generally large group of people in the form of an open call. This concept is especially appealing to be used in emergency situations in order to obtain fast and widely-distributed information over the entire affected region, which allows at the end performing suitable risk management actions. Given an emergency event (fires, floods, earthquakes, hurricanes, etc.), ordinary or trained habitants can collaborate gathering the necessary data that after some processing will reach the hands of decisions makers and help them coordinate the mitigation actions. The sense of contribution or collaboration encourages the people to work more and better, ending up in a relatively fast and low-cost process. One of the best examples is the production of intensity maps after an earthquake (e.g. USGS) with information gathered from internet forms; filled out by affected habitants according to what they had seen or felt at their location at the moment of the event. In this manuscript, the focus is on assessing the usefulness of the data generated from crowdsourcing for earthquake damage assessment on buildings. A small set of photographs was purposely taken in a selected area of Christchurch, New Zealand by two persons a few days after the earthquake. This dataset is used to study the technique with an engineering and geophysicist point of view, and the pros and cons of it are analyzed and briefly discussed, having also in mind a possible comparison of ground assessments with possible satellite data on the same area.