Coseismic offsets due to the 11 April 2012 Indian Ocean earthquakes (M_w 8.6 and 8.2) derived from GPS measurements

Abstract

The 11 April 2012 earthquake (Mw 8.6) in the Indian Ocean, about 100 km west off the Sumatra subduction zone, is the largest intraplate strike‐slip earthquake in the known history. Two hours later, it triggered another great earthquake of Mw 8.2 in its vicinity. The earthquakes reflect the internal deformation of the diffused plate boundary between India and Australia caused by the differential plate motion between them. The slip occurred on conjugate planes, and the presence of some of them has been reported from the swath bathymetry and satellite magnetic anomalies. We estimate coseismic offsets due to these earthquakes at continuous GPS sites in the Andaman‐Nicobar region and at other International GNSS Service (IGS) sites around the earthquakes source region. The sites on the Andaman Islands, which are about 900–1200 km to the north of the earthquake epicenters, experienced predominantly southward coseismic offset of up to 3 cm. The nearest site, Campbell Bay, on Great Nicobar Island, about 500 km to the north of the earthquake, documented an ESE offset of about 4 cm. The coseismic offsets are consistent with the finite‐fault slip models derived from back projection of the seismic waves recorded by the global networks.

Did Anthropogenic Activities Trigger the 3 April 2017 Mw 6.5 Botswana Earthquake?

“…In 2001, the Indian region of Gujarat was affected by a strong Mw 7.7 intraplate earthquake, causing more than 20,000 casualties [9]. Finally, in 2012, the largest known strike-slip intraplate earthquake (Mw 8.6) occurred in the Indian Ocean, about 100 km SW of the Sumatra subduction zone [10]. With respect to the more common earthquakes occurring at plate boundaries, intraplate earthquakes are poorly understood as most of them are not easily ascribable to any identifiable or prominent fault zone.…”

Co-seismic offsets due to two earthquakes (M w 6.1) along the Sumatran fault system derived from GNSS measurements

“…Seismicity map is based on BMKG (Agency for Meteorology, Climatology and Geophysics) database (lower detection limit is approximately M w 4.5). b Coseismic offsets resulting from the April 11, 2012 earthquake derived from AGNeSS (blue arrows) and two previous studies (gray arrows) (Yadav et al 2013;Hill et al 2015). Ishii et al 2013).…”

“…Ishii et al 2013). Previous studies (Yadav et al 2013;Hill et al 2015) reported co-seismic offsets around the Andaman-Nicobar GNSS network, which includes the Sumatran GNSS Array (SuGAr) and IGS sites. The AGNeSS also observed horizontal co-seismic offsets ( Table 1).…”

“…However, the vertical offsets were very small (∼1 cm); thus, we reported only the horizontal offsets at the AGNeSS site. Figure 1b shows the horizontal displacements from the GNSS sites, which consisted of AGNeSS (blue arrows), SuGAr, and IGS sites (gray arrows) (Yadav et al 2013;Hill et al 2015). These offsets contained the effects of both the M w 8.6 sequence and the M w 8.2 aftershock.…”

Visualization of attenuation structure and faults in incoming oceanic crust of the Nankai Trough using seismic attenuation profiling

“…Therefore, it is important to identify the presence, size and activity extent of seismic faults for prevention and mitigation of earthquake-related disasters. Investigation of intracrustal faults is important not only to understand their relationships with intracrustal earthquakes (e.g., Yadav et al 2013) but also the contribution of fluid interactions between the mantle and crust in generating earthquakes (e.g., Sano et al 2014).…”