Temporal profiling of uplift rate along an active fault using river long profile in the Kuchchh region, Western India

Abstract

River long profiles are widely used as tectonic event markers. Incision/uplift rate estimations based on the dating of river terrace or exposed scarp sediment give long-term averaged uplift rate values with the limitation of not giving the intermediate phases of highs and lows. On the other hand, GPS based estimates provide only decadal-scale uplift rate estimates. In our study, we adopted the long profile inversion methodology to obtain a temporal profile of uplift rate history (over the Late Pleistocene-Holocene time period) along an active fault (the Kuchchh Mainland Fault) in Kuchchh region, western India, which has experienced several large magnitude earthquakes in recent past. We also used long profiles analysis to quantify the transient response of Kuchchh landscape to uplift activity along the Kuchchh Mainland Fault. Steepness index and chi profiles were estimated to display the spatial variability in landscape disequilibrium. Integral method-based chi profiles were used to obtain the optimum value of basin area exponent of the Stream Power Incision Model (SPIM). Our estimates provide a mean uplift rate value of 1.1–1.4 mm/yr along the Kuchchh Mainland Fault during the Late Pleistocene-Holocene period, which matches with the average uplift rate derived from other independent observations in this region. Further, a chronology of major tectonic phases from the estimated uplift rate time series also corroborates with field-based estimates of major incision events in Kuchchh region. We also tested the robustness and sensitivity of our uplift rate estimates to model parameters. Such data can be complementary to the existing sparsely (both spatially and temporally) distributed uplift rate database, which is imperative to seismic hazard assessment.