The rapid progress of development in the Surabaya area, especially in areas crossed by the Waru segmentation fault, Wiyung District, and Lakarsantri, is marked by the number of residential developments and tall buildings which will certainly contribute to the value of natural disaster vulnerability, earthquakes. So, to reduce the risk value of loss to casualties and material losses from potential earthquakes, further mitigation is needed. The aim of this study is to determine the dominant factors for building vulnerability and earthquake natural disaster mitigation in the Waru segmentation fault area. One of the analytical methods used is the Importance Index (IMPI) method, this analysis method is carried out to determine the most dominant risk level from existing risks and bowtie analysis is used to manage, reduce and mitigate the most dominant risks. Based on the results of research and risk assessment, the most dominant risk level variable for building vulnerability due to Waru segmentation faults is variable 2 c (finishing with heavy loads such as concrete or precast panels that are not firmly attached to the structure) with an IMPI value of 83.13 %. The presence of finishing with heavy loads such as concrete or precast panels that are not firmly attached to the structure in the event of an earthquake disaster in the Waru Fault will endanger and can bring down people around the building. To reduce the risk of casualties due to earthquakes in the Waru Fault, it is necessary to prevent by providing an additional number of dynabol bolts, enlarging the reinforcement at the façade and canopy joints, locking concrete cavities with special concrete stucco additives and conducting surveillance monitoring during construction
