Uncertainty of microseismic monitoring results can be reduced to improve hydraulic fracture modeling. A computing device can use a fracture model to determine a predicted geometry of a hydraulic fracture in a subterranean formation based on properties of a fracturing fluid that is introduced into the subterranean formation. An uncertainty index of the predicted geometry of the hydraulic fracture can be determined based on an uncertainty value of the predicted geometry and a trend of uncertainty values. When the injection flow rate of the fracturing fluid is less than a maximum flow rate, it can be increased from an initial injection flow rate to an increased injection flow rate in response to determining the uncertainty index exceeds a pre-set maximum.