Passive source seismic imaging delineates fine crustal and lithospheric structures associated with the Kachchh rift zone (KRZ), Gujarat, India, which suggests a 4-7 km crustal thinning and 6-12 km asthenospheric thinning below the KRZ relative to surrounding regions. The study also depicts a constant lithospheric thickness (~76-78 km) below the median high towards the west of Kachchh rift zone while a marked decrease in lithospheric thickness as well as shear velocity (Vs) is noticed across west to east and south to north of the rift zone, which perhaps suggests an increase in partial melt contents below the central KRZ in comparison to surrounding regions. Further, we notice that the seismogenic zone extends up to 34 km depth below the central KRZ. The hypocenters of the Bhuj 2001 earthquake sequence are found to be mainly concentrated in the mafic-to-ultramafic lower curst (14-34 km depth) below the central KRZ. The coincidence of common area of crustal thinning, asthenospheric upwarping and confined aftershock activity suggests that there is a possible causal relation between the occurrences of continued aftershock activity and a 6-10% drop in Vs (or presence of carbonatite melts) at lithosphere-asthenosphere boundary (LAB) below the central KRZ. This 6-10% drop in Vs can be attributed to a ~1-2% carbonatite melt currently present at the LAB. Thus, we interpret that the presence of aqueous fluids (released during the prograde metamorphic reactions of lower crustal olivine-rich rocks) and volatile CO2 [emanating from the crystallization of carbonatite melts at shallow upper mantle depths (i.e. 50-70 km)] at the hypocentral depths, might be playing a key role in generating the 2001 Bhuj earthquake sequence covering the entire lower crust.
Imaging of the Crust and Upper Mantle Structure below the Kachchh Rift Zone, Gujarat, India, through Passive Source Seismic Studies
₹100.00
Passive source seismic imaging delineates fine crustal and lithospheric structures associated with the Kachchh rift zone (KRZ), Gujarat, India, which suggests a 4-7 km crustal thinning and 6-12 km asthenospheric thinning below the KRZ relative to surrounding regions. The study also depicts a constant lithospheric thickness (~76-78 km) below the median high towards the west of Kachchh rift zone while a marked decrease in lithospheric thickness as well as shear velocity (Vs) is noticed across west to east and south to north of the rift zone, which perhaps suggests an increase in partial melt contents below the central KRZ in comparison to surrounding regions. Further, we notice that the seismogenic zone extends up to 34 km depth below the central KRZ. The hypocenters of the Bhuj 2001 earthquake sequence are found to be mainly concentrated in the mafic-to-ultramafic lower curst (14-34 km depth) below the central KRZ. The coincidence of common area of crustal thinning, asthenospheric upwarping and confined aftershock activity suggests that there is a possible causal relation between the occurrences of continued aftershock activity and a 6-10% drop in Vs (or presence of carbonatite melts) at lithosphere-asthenosphere boundary (LAB) below the central KRZ. This 6-10% drop in Vs can be attributed to a ~1-2% carbonatite melt currently present at the LAB. Thus, we interpret that the presence of aqueous fluids (released during the prograde metamorphic reactions of lower crustal olivine-rich rocks) and volatile CO2 [emanating from the crystallization of carbonatite melts at shallow upper mantle depths (i.e. 50-70 km)] at the hypocentral depths, might be playing a key role in generating the 2001 Bhuj earthquake sequence covering the entire lower crust.
Publication Mode |
Online |
---|---|
Publication Author |
Prantik Mandal |
Publication Language |
English |
Publication Type |
Conference Paper |
Publication Year |
2016 |
You must be logged in to post a review.
Reviews
There are no reviews yet.