The treatment of basal sliding is one of the most important ingredients in models of glaciers and ice sheets. However, basal sliding is notoriously difficult to observe. Although boreholes and laboratory studies offer insight into the physics of sliding, they represent localized and idealized conditions respectively. Basal icequakes offer a window into this challenging observational environment. Here, we seek to falsify the hypothesis that basal shearing-mode icequakes indicate basal sliding. We examine passive seismic datasets from the Rutford Ice Stream (RIS) and the West Antarctic Ice Sheet Divide (WAIS Divide). High-frequency impulsive seismic events are abundant in the RIS dataset as described by Smith et al. (2015) but appear absent in the WAIS Divide dataset. To quantify this pattern, we create an icequake catalog using a standard Short-Time-Average / Long-Time-Average (STA/LTA) event detection algorithm. Our preliminary effort to catalog icequakes at the WAIS Divide site results in no clear detections. This result is consistent with the hypothesis that basal shearing-mode icequakes indicate basal sliding. We interpret the lack of basal icequake activity at the WAIS Divide site using the model of Lipovsky (2019). We propose the existence of an ice sheet aseismic zone that includes regions of the ice sheet where basal icequakes are not observed. Future observations could greatly refine the boundaries of this aseismic zone. Given the high sensitivity of basal icequakes to environmental conditions, an improved knowledge of the ice sheet aseismic zone has the potential to offer new insights into the onset of glacier sliding (c.f., Mantelli et al., 2019), subglacial geology, subglacial water flow, and ice sheet evolution.