Imaging of a magma system beneath the Merapi Volcano complex, Indonesia, using ambient seismic noise tomography

Abstract

Summary Mt. Merapi, which lies just north of the city of Yogyakarta in Java, Indonesia, is one of the most active and dangerous volcanoes in the world. Thanks to its subduction zone setting, Mt Merapi is a stratovolcano, and rises to an elevation of 2968 m above sea level. It stands at the intersection of two volcanic lineaments, Ungaran–Telomoyo–Merbabu–Merapi (UTMM) and Lawu–Merapi–Sumbing–Sindoro–Slamet, which are oriented north-south and west-east, respectively. Although it has been the subject of many geophysical studies, Mt Merapi's underlying magmatic plumbing system is still not well understood. Here, we present the results of an ambient seismic noise tomography study, which comprise of a series of Rayleigh wave group velocity maps and a 3-D shear wave velocity model of the Merapi-Merbabu complex. A total of 10 months of continuous data (October 2013–July 2014) recorded by a network of 46 broadband seismometers were used. We computed and stacked daily cross-correlations from every pair of simultaneously recording stations to obtain the corresponding inter-station empirical Green's functions. Surface wave dispersion information was extracted from the cross-correlations using the multiple filtering technique, which provided us with an estimate of Rayleigh wave group velocity as a function of period. The group velocity maps for periods 3–12 s were then inverted to obtain shear wave velocity structure using the neighbourhood algorithm. From these results, we observe a dominant high velocity anomaly underlying Mt. Merapi and Mt. Merbabu with a strike of 152° N, which we suggest is evidence of old lava dating from the UTMM double-chain volcanic arc which formed Merbabu and Old Merapi. We also identify a low velocity anomaly on the southwest flank of Merapi which we interpret to be an active magmatic intrusion.

3-D shallow shear velocity structure of the Jakarta Basin from transdimensional ambient noise tomography

“… 2020 ; Yudistira et al . 2021 ) also illustrate this dominance of the ambient seismic noise wavefield by sources in the Java Sea.…”

Modeling of subsurface structure by using magnetic methods in the area of Mt. Pandan, Indonesia

“…At a depth of approximately 2.3 km from mean sea level, the shear wave velocity increases. This has been interpreted as evidence of consolidated igneous rock or magmatic intrusive bodies (e.g., Young et al 2013;Crowder et al 2019;Yudistira et al 2021). At a depth of 8.5 km from mean sea level, the shear wave velocity decreases, which is probably related to the presence of a magma chamber that supplies magma to Mount Wilis and Mount Pandan; information from Santoso et al (2017) reports that in the Mount Pandan area, an earthquake occurred, which is interpreted in terms of tectonic activity or magma movement or both.…”

Generating 1D depth profile of shear-wave velocity from ambient noise cross-correlation: application to Jakarta array

“…For almost a decade, surface wave tomography based on cross-correlations of ambient seismic noise has dramatically improved our knowledge of regional crustal structure in Indonesia ( [1][2][3][4][5][6], among others). The stack of cross-correlations between a 2-station pair, i.e., the noise correlation function (NCF), represents empirical Green's function and comprises the information of the subsurface structure between those stations.…”