Investigation of Subsurface S-wave Velocity Structures beneath a Mud Volcano in the Matsudai-Murono District by Surface Wave Method

Vertical movements of the Murono mud volcano in Japan caused by the Naganoken Kamishiro Fault Earthquake in 2014

“…Onishi et al 2009;Matta et al 2012) and has also been recognized as an uplift area during the quiescent phase (Kusumoto et al 2014). Despite the small size of the mud volcano, it is interesting that the conspicuous uplift due to neighbouring large earthquakes occurred at the specific area and that the area undergoes an uplift during the quiescent phase; during this phase, a repetition of uplift and subsidence is observed within a period of around a month.…”

“…Chigira and Tanaka 1997;Panahi 2005;Mellors et al 2007;Davies et al 2008;Manga et al 2009;Mazzini et al 2009b;Sawolo et al 2009Sawolo et al , 2010. The Murono mud volcano, studied by us (Figure 1), is no exception; a local GPS survey detected a vertical movement of 400 mm caused by the Niigataken Chuetsu-oki Earthquake in 2007 (Figure 1, M = 6.8) (Onishi et al 2009). In addition, Matta et al (2012) observed an elliptical uplift area, reaching a maximum height of 400 mm, through Lidar survey after the 2011 Naganoken Hokubu Earthquake (Figure 1, M = 6.7).…”

“…Given the past observational evidences mentioned above and due to a probability of occurrence of a similar type of movements as shown by Onishi et al (2009) and/or Matta et al (2012), we have carried out a periodic, precise levelling since 2012 to i) observe interseismic vertical movements as an indication of the status of the mud volcano at rest and ii) examine the source of any conspicuous vertical movements (Kusumoto et al 2014). This year, we conducted the scheduled levelling in June and November.…”

Vertical movement during the quiescent phase of the Murono mud volcano, Niigata, Japan

“…Vertical movements observed by local Global Positioning System (GPS) surveys in the Murono mud volcano area before and after the Niigataken Chuetsu-oki earthquake in 2007 (Figure 1, Mw = 6.6; e.g., Imanishi and Kuwahara 2009) have reached approximately 400 mm (Onishi et al 2009). Onishi et al (2009) suggested that this conspicuous vertical movement was caused by the effects of this earthquake on the mud volcano, but other conspicuous crustal movements due to this earthquake were not observed by the regional GPS network operated in this area by the Geographical Survey Institute of Japan (GSIJ). The distance between the epicenter and the mud volcano area was about 44 km, and these data highlight that it is important to understand the behavior of the Murono mud volcano in response to neighboring large earthquakes.…”

“…This sedimentary basin, which is known as the Niigata basin, has many fold structures in the NE-SW direction and is one of the most important petroleumproducing areas in Japan. Thus, this mud volcano has been investigated by numerous researchers from geophysical and geochemical perspectives (e.g., Onishi et al 2009;Shinya and Tanaka 2009;Suzuki et al 2009;Etiope et al 2011).…”