Fig. 1: Networks summarize human movements between census tracts.
a Visualization of observed movements from home neighborhoods to hospitals in Harris County, TX, during the storm week beginning on February 15, 2021 (Monday). Home locations are recorded using U.S. census block groups (which we enumerate CBGi and which comprise larger spatial units called census tracts), whereas destination locations are points of interest (POIs) with known latitudes, longitudes, and other information such as industry category (e.g., hospitals). b For different industry categories, we construct networks that are each encoded by a time-varying adjacency matrix in which Aij(t) encodes movements from one census tract to another, CTi → CTj, where CTi is a person’s home census tract, and they visit a POI in census tract CTj during week t. We also study movements in and out of census tracts defined by their node degrees: \({d}_{i}^{\mathrm{in}}(t)={\sum }_{j}{A}_{ji}(t)\) and \({d}_{i}^{\mathrm{out}}(t)={\sum }_{j}{A}_{ij}(t)\).
