The versatility and low energy consumption of Wireless Sensor Networks (WSN), makes this technology a potential tool for the development of large-scale networks, where access to communication services and energy consumption present some limitation. Because of this, it becomes a potential solution for development of post-seismic alarm networks. The registration of the maximum acceleration peaks, that could be experiment by building structures after an earthquake, could be used to help to identify potentially affected areas after the occurrence of a seismic event. However, the number of message that could be generated in the network could affect the effective delivery of reported data. Because message congestion could become a critical factor that affect the successful delivery of data over the network. In this paper, is being shown a performance evaluation of a post-seismic assessment solution through different scenarios where load balancing Load-Aware On-Demand Routing (LAOR) and Flooding protocols were analyzed, as well as the use of a mechanism to desynchronize the send of messages in the network, based on the Backoff Algorithm of IEEE 802.15.4 Standard. An additional Backoff time called WT is also proposed for network desynchronization to achieve some improvement in the network QoS. The simulation results show that our proposal significantly improve performance on both protocols. The different scenarios that were evaluated considered the possibility of the collapse of some buildings after a strong or moderate magnitude event and the effect that this fact can introduce in the message traffic through the network in a seismic event conditions.