Data repository for the paper "Tectonics and seismicity in the Northern Apennines driven by slab retreat and lithospheric delamination"

Output data from a numerical modeling study analyzing the Tectonics and seismicity of the Northern Apennines in relation to the geodynamic mechanism (slab retreat and crustal delamination) suggested to be driving the orogenic system.

Understanding how long-term subduction dynamics relates to short-term seismicity and crustal tectonics is a challenging but crucial topic in seismotectonics. We attempt to address this issue in the context of the Northern Apennines orogenic belt, which displays characteristic tectonic and seismogenic behaviors on a wide range of spatiotemporal scales. We use a visco-elasto-plastic seismo-thermo-mechanical (STM) modeling approach with a realistic 2D setup based on available geological and geophysical data. In accordance with regional geodynamics, subduction dynamics and seismicity are simulated together, driven solely by slab pull. Our numerical experiments suggest that lower crustal rheology and lithospheric mantle temperatures modulate the crustal tectonics of the Northern Apennines. Results indicate that the observed spatial distribution of the upper crustal tectonic regimes requires buoyant and highly ductile material beneath the suture zone. This allows protrusion of the asthenosphere in the lower crust, lithospheric delamination, and slab retreat. The resulting horizontal velocities and principal stress axis orientations agree with observations, suggesting that slab delamination and retreat are compatible with regional deformation. Our simulations successfully reproduce the presence of seismicity in the thrust front and on normal faults in the interior of the range. Slab temperatures and lithospheric mantle stiffness distinctly affect the cumulative seismic moment release and the spatial distribution of upper crustal earthquakes. The properties of deep, sub-crustal material are thus shown to influence model shallow seismicity, even though the upper crust is largely mechanically decoupled from the lithospheric mantle. Our simulations therefore highlight the important effect of deep crustal rheologies and self-driven subduction dynamics in controlling the shallow, brittle deformation and related seismicity during an ongoing orogeny.

The repository consists of the following: 1) the executable code for running the model (i2_istm and in2_istm, the latter of which is used to initialise the model); 2) the setting files for which timesteps to output (mode.t3c and mode_istm.t3c, the latter of which is for the short-term phase of the model), the model setting files (init_istm.t3c), rock type and temperature setup images (prf_app.tif and tfin.tif, respectively); and 3) the output quantities in the model for the last timestep in HDF5 format (app400.gzip.h5), the list of ruptured markers (pick_events_app.txt) and GPS-station-like markers at the surface (eachdt_gpsmarker_app.txt), and the time limits used for computing average velocities from the GPS marker positions (timelims.mat).

The files used for the figures in the paper relate to the reference model and 9 other models: 2 models with different rheology for the Adriatic lower crust, 2 models with different temperatures in the mantle, and 5 models with different shear modulus in the Adriatic lithospheric mantle. The two models with different lower crust rheology (granulite and plagioclase) were not run in short-term mode and therefore no GPS-like or ruptured markers logs are available for them. Descriptive prefixes are used to identify which model each file refers to. The rock type setup is common to all models included here. The reference temperature setup is also used for the models with different shear modulus in the slab and the model with granulite lower crust rheology. The model with plagioclase lower crust rheology has a different temperature setup with a hotter lower crust, as mentioned in the paper; it is not a simple exploration of the effect of rheology, but an attempt to get the lower crust to be very ductile through a combination of a ductile rheology (but less so than in the reference model) and high temperatures.

For information about the modeling code, setup, results, and interpretation, please refer to the paper. This repository will be updated with the final paper information after publication.