## 2 LiCSAR System Architecture
### LiCSAR Earthquake InSAR Data Provider  
The rapid availability of Sentinel-1 data following acquisition (a few hours), together with the short revisit period, for many areas, of 6 days, provides a unique opportunity to develop an automatic earthquake response system using the LiCSAR infrastructure. The main objective of this response system is to form co-seismic interferometric pairs in a rapid manner, as well as pre- and post-seismic interferograms, and to make these data widely and freely available to the community. We anticipate that these products have applications for the scientific understanding of events as well as for operational crisis management and disaster mitigation. The automatic Earthquake InSAR Data Provider (EIDP) within the LiCSAR system works as follows (Figure 6): a list of current earthquake events with a minimum magnitude of \(M_{w}\) 5.5 is requested through a libcomcat python library [56] providing access to the USGS Comprehensive Earthquake Catalog (ComCat). We then generate a look-up table to estimate the potential radius of the region in which surface deformation caused by the earthquake may have occurred, given the estimated seismological magnitude and 3D location of its hypocentre, accounting for uncertainties in the seismological estimates (see Table 1). This surface radius is used to select all overlapping frames, using the frame definitions from the LiCSInfo database. In the case that a selected frame has not beenpreviously initialised, an automatic initialisation is attempted. We then update the EIDP-related tables in the LiCSInfo database and process at least the last month of data associated with the selected frames using standard LiCSAR parameters and the LiCSAR FrameBatch approach. We have developed routines for the early identification and fast download of the first post-earthquake Sentinel-1 data and we have created an automatic download routine that uses the Copernicus SciHub service as an alternative data source in order to ensure the availability of the latest data for processing--Sentinel-1 SLC data typically arrive at Copernicus SciHub within a few hours post acquisition, which is earlier than they appear in other accessible data mirrors. As we use image cross-correlation algorithms within the LiCSAR coregistration step (see Figure 3), the RSLCs can be generated successfully even without the use of precise orbital ephemerides. Instead, restituted ephemerides (existing already at the time of appearance of the source Sentinel-1 data) are downloaded and applied automatically. We also export co-seismic interferograms as Google Earth KMZ files, in addition to standard InSAR outputs. After a basic quality check, we link the co-seismic interferogram products to our web-based LiCSAR EIDP map and prepare structures for their automatic ingestion to other community systems (see Section 3). We also aim towards integration of GACOS atmospheric phase screen correction estimates to the final interferograms, noting that GACOS data should be available with a 24 h delay. From the perspective of the system architecture, we have been using a sequential procedure that generates coseismic interferograms within 24 h after the post-event SAR data acquisition. This has been lately substituted by a solution that allows us to reach co-seismic interferograms within 1-3 h after the appearance of post-event Sentinel-1 SLC data on the Copernicus SciHub web service. The major difference is a specific integration of a dedicated computing node at a distant computing \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Magnitude [\(M_{\text{up}}\)]**} & **Max. Depth of** & **Surface Effect Radius** & **Postseismic InSAR [Days** \\  & **Hypocentre [km]** & **from Epicentre [km]** & **after Earthquake Event]** \\ \hline
5.5–5.9 & 10–16 & 20–30 & 18–36 \\
6.0–6.9 & 18–63 & 36–167 & 30–84 \\
7.0–7.9 & 73–250 & 199–938 & 54–132 \\
8.0–8.5+ & 250 & 1115–2500 & 108–156 \\ \hline \end{tabular}
\end{table}