Abstract: Structural identification plays an important part in the monitoring of sensitive structures such as onshore wind turbines. Due to the nature of wind, such structures are subjected to turbulent wind fields that cause aerodynamic excitations to the structure. Such turbulent wind fields are hard to be measured, thus output-only identification is required. Output-only identifcation is a hard category of structural identification methods that is used whenever input excitations are unknown or hard to be measured. With their ability to estimate and reproduce the excitation histories, output-only has established itself as an important method in structural health monitoring. This contribution utilizes a previously developed simplified model to perform an output-only identification to onshore wind turbine towers. The studied wind turbine is an idling 5-MW reference turbine developed by the National Renewable Energy Laboratory (NREL). The effect of the number of sensors distributed on the tower was studied, and obtained results were satisfying in both identification accuracy and force estimation, encouraging to improve the identification scheme by coupling it with a noise filtering method to deal with noisy vibration responses.