<p>Despite the well-established interest of Synthetic Aperture Radar data for volcanoes study and monitoring, their integration to operational monitoring activities in volcanoes observatories remains limited so far. We here describe the effort in progress to integrate in near real time the information derived from Sentinel-1 satellites into the monitoring devices at BBPTKG in charge of Merapi volcano survey as well as the use of Sentinel-1 data during the recent period of &#160;unrest. Merapi (7&#176;32.5&#8217; S and 110&#176;26.5&#8217; E) located in the densely populated Province of Yogyakarta in Central Java is one of the most active volcanoes in Indonesia. The eruptive history of Merapi is characterized by two eruptive styles: 1) recurrent effusive growth of viscous lava domes, with gravitational collapses producing pyroclastic flows known as &#171; Merapi-type nu&#233;es ardentes &#187; (VEI 2); 2) more exceptional explosive eruptions of relatively large size (VEI 3-4), associated with column collapse pyroclastic flows reaching distances larger than 15 km from the summit. The eruptive periodicity is 4 to 5 years for the effusive events and 50 to 100 years for the explosive ones. The last explosive events (VEI 3-4) occurred in November 2010 and was followed by a period of limited activity. In August 2018, a new dome was observed inside the summit crater, thus marking the start of a new phase of effusive activity. A new period of unrest then started in mid-October 2020, characterized by an increase in seismic activity as well as large and localized displacements in the summit area. Magma finally reached the surface on 4<sup> &#160;</sup>January 2021. Deformation is currently recorded by EDM and tiltmeters together with a network of 10 permanent GNSS stations. GNSS data are automatically processed and inverted for a pressure source at depth. Both displacement time series as well as spatial probability distribution are directly available through WebObs (Beauducel et al., Frontiers, 2020), an integrated web-based system for monitoring. Sentinel-1 data are acquired over the volcano every 12 days on descending track 76 and every 6 days on ascending track 127. Since mid 2017, Sentinel-1 data are automatically downloaded on a local server at BPPTKG. Interferograms and coherence images are then produced using the NSBAS processing chain (Doin et al, 2012) and automatically integrated to WebObs to enable detection of potential rapid and significant changes in signal. Mean velocity maps are also produced as well as time series of surface displacement at given location enabling direct comparison with GNSS measurements. The descending InSAR time series shows a strong displacement away from the satellite in a 1.5 km wide area located on the north-eastern part &#160;of the crater. This signal became significant in September 2020. It is consistent with field measurements recorded and allows to map the affected area. In mid-November 2020, Sentinel-1 data thus provided the first information on the spatial extent of the ongoing surface displacements, which was useful for crisis management.</p>
Abstract Magma ascent rate can control the hazard potential of an eruption, but it is difficult to directly determine. Here we investigate the variations in timescales of magma ascent and rates of magma ascent for the three most recent explosive and effusive eruptions of Kelud volcano in Indonesia (1990, 2007, and 2014) using the zoning of volatile elements (OH, Cl, F) in apatite. We found that crystals from the 2007 dome show chemical gradients and increasing concentrations (reverse zoning) in chlorine and/or fluorine towards the crystals’ rims whereas those of the 1990 and 2014 explosive eruptions are unzoned. Diffusion modelling of the volatile elements in zoned apatite of the 2007 dome rocks give magma ascent times of up to 3 months, although 71% of them are ≤ 60 days. In contrast, the maximum magma ascent timescales inferred from apatite of the 1990 and 2014 explosive eruptions are about 7–8 hours. Using the pre-eruptive magma storage depths obtained from petrological and phase equilibria studies, we calculate ascent rates of about > 0.4 × 10 − 3 m s − 1 for the 2007 dome, and > 2.6 × 10 − 1 m s − 1 for the 1990 and 2014 eruptions. We also calculated the magma viscosities for each eruption, which when combined with the magma ascent rates and magma mass discharge rates correspond well with the expected eruptive styles. Our study illustrates the robustness of modelling apatite zoning in volatile elements to constrain timescales and magma ascent dynamics, and highlights the important role of magma ascent on eruptive styles.
ABSTRAK Sejak awal Maret 2014 status aktivitas Gunung Api Slamet di Jawa Tengah dinaikkan dari normal (level I) menjadi waspada (level II) seiring dengan peningkatan jumlah gempa vulkanik. Seismisitas Gunung Api Slamet yang dipantau melalui empat stasiun seismik memperlihatkangempa letusan terekam sebanyak 1.106 kejadian dengan rata-rata 73 kejadian per hari, gempa hembusan terekam sebanyak 6.857 kejadian dengan rata-rata 457 kejadian per hari, sedangkan gempa vulkanik dalam (VA) hanya terekam sebanyak 2 kali selama periode Maret – Agustus 2014. Sumber gempa tersebut berada pada kedalaman antara 1 - 2 km di bawah kawah Gunung Api Slamet sebagai indikasi gempa permukaan. Peningkatan aktivitas magmatik tersebut menghasilkan pelepasan gasCO2 yang berpengaruh terhadap fluida panas bumi yang ditunjukkan dengan terjadinya perubahan keasaman air dari normal menjadi alkalin, pembentukkan bualan gas CO2 pada air panas Pancuran 3 di Baturraden, dan peningkatan saturasi kalsit. Bualan gas CO2 pada air panas Pancuran 3 menjadi indikasi terjadinya proses pendidihan pada temperatur 273° C pada elevasi kedalaman 454 m dibawah permukaan laut. Kondisi ini menjadikan temperatur reservoar menjadi lebih tinggi sebagai indikasi bahwa sistem panas bumi Gunung Api Slamet merupakan sistem panas bumi aktif (active geothermal system) bertemperatur tinggi (high enthalpy). Kata kunci : bualan gas, fluida panas bumi, gempa permukaan, saturasi kalsit ABSTRACT Since the beginning of March 2014 the activity status of The Slamet Volcano in Central Java has been declared from normal (level I) to become alert (level II) due tosignificant increase in the number of volcanic earthquakes. The Slamet Volcano seismicity monitored by four seismic stations shows eruption earthquakes as many as 1,106 events with an average of 73 events per day, gas emission earthquakes as many as 6,857 events with an average of 457 events per day, whereas the deep volcanic (VA) earthquake recorded only 2 times during the period of March to August 2014. The hypocentre of these earthquakes was at a depth of 1-2 km below Slamet Volcano crater as an indication of surface earthquakes. Increased magmatic activity resulted in the release of CO2 gas effect on the geothermal fluid indicated by changes in water acidity from normal to alkaline, formation of CO2bubblegas on Pancuran 3 hot springat Baturraden area, and calcite saturation enhancement. The presence of CO2 bubble gas on Pancuran 3 hot springis an indication of a boiling process at the temperature of 273° C at a depth of 454 m below sea level. This condition makes the reservoar temperature becomes higher as an indication that the geothermal system of The Slamet Volcano is an active geothermal systemwith high temperature (high enthalpy). Keywords: bubble gas, geothermal fluid, surface earthquake, calcite saturation
We present the combination of permutation entropy (PE) and power spectral density (PSD) analysis on continuous seismic data recorded by short-period seismic stations during the 2010 Merapi volcano eruption. The calculation of PE aims at characterizing the randomness level in seismic noise, while the PSD parameters use to detect the background noise level in various frequency bands. It was previously observed that a significant reduction of randomness before the volcano eruption could be indicated as one of the short-term precursors due to the lack of high frequencies (>1 Hz) in the noise wave-field caused by high absorption losses as the hot magma uprises to the upper crust. The results show no significant reduction in signal randomness before the eruption series. The characteristic of events during the preeruptive period and the crisis tends to be chaotic (PE in the range 0.9 to 1). Further calculations show that the standard deviation in PE decreased in four days before the first eruption onset on 26 October. PE was stable at the highest values (very close to 1) and gradually returned to the previous fluctuation after the eruption onset. The level of background noise in the low- and high-frequency bands appeared to have the same tendency. The two main eruptions correspond to the two highest peaks of noise levels.
Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at G-Cubed. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]The Role of Magma Storage Conditions and Excess Fluids in the Effusive to Explosive Eruption StylesAuthorsSri BudhiUtamiiDJoanAndujarFidelCostaiDBrunoScailletHanikHumaidaSee all authors Sri Budhi UtamiiDCorresponding Author• Submitting AuthorNanyang Technological UniversityiDhttps://orcid.org/0000-0003-4338-0157view email addressThe email was not providedcopy email addressJoan AndujarCNRS Universite d'Orleansview email addressThe email was not providedcopy email addressFidel CostaiDNanyang Technological UniversityiDhttps://orcid.org/0000-0002-1409-5325view email addressThe email was not providedcopy email addressBruno ScailletISTO - UMR 6113 CNRSview email addressThe email was not providedcopy email addressHanik HumaidaGeological Agency of Indonesiaview email addressThe email was not providedcopy email address
<p>The 2010 eruption of Merapi produced pyroclastic deposits and lava flows that are compositionally very similar, raising the question as to the underlying reason of the differences in eruptive styles between the various phases of the 2010 eruptive events. To test whether primary magmatic volatile content is the reason for the different eruption styles, we analyzed magmatic water contents in nominally anhydrous clinopyroxene crystals contained in lava and ash from the 2010 eruptive events. We utilized two analytical approaches: (i) Fourier-transform infrared spectroscopy (FTIR) analysis of fresh clinopyroxene from the ash and lava samples and (ii) FTIR analysis of clinopyroxene both prior to and after experimental re-hydration. By employing calculated partition coefficients, we determined the magmatic water content of the magma from which the various crystals grew. The magmatic water content determined from the unmodified clinopyroxenes from lava samples yield a range of 0.35 wt.% to 2.02 wt.% H<sub>2</sub>O, whereas magmatic water contents determined from untreated clinopyroxene contained in the ash samples range between 0.04 and 3.25 wt.%, with two outliers at 4.62 and 5.19 and wt.%, respectively. In contrast, for the rehydrated crystals the range for lava derived clinopyroxene crystals is between 1.94 and 2.19 wt.% and for ash between 1.74 and 2.66 wt.%, with two crystals at extreme values of 0.85 and 3.20 wt.%. We interpret these results to indicate that crystals from different populations are present in the 2010 eruptive products, with the dominant group reflecting relatively low magmatic H<sub>2</sub>O contents (around 2 wt.%) due to storage in shallow magma reservoirs and pockets at high levels within the Merapi plumbing systems (e.g. top 3 km). The overall higher H<sub>2</sub>O range and the occasionally more extreme values recorded in clinopyroxenes from ash deposits may then represent the presence of a crystal population that last equilibrated at deeper levels and at higher water contents, i.e. these crystals derive from the replenishing magma that activated the shallow portion of the plumbing system during the 2010 events. While this is work in progress, our results so far seem to suggest that the pyroclastic deposits of the 2010 Merapi eruption may contain a higher fraction of clinopyroxene derived from &#8216;deeper magma&#8217; with higher H<sub>2</sub>O contents then what we have detected in associated lavas.</p>
Very low-to low-grade metamorphic rocks in Karangsambung area are widespread in the Northern
Part of Luk UloMelangeComplex especially in Gebang River, Kaliwiro Area, Central Java.This
research was conducted in order to understand [1] P and Tcondition of metamorphic rock, [2] protolith
variation, [3] relation between these rocks and other rock units, and [4] tectonic environment pre- and
syn-metamorphism. The systematic sampling method was conducted to record mineralogical change
along Gebang River using petrography, XRD, XRF, and SEM-EDS analyses. Several rocks
werecropped outs,whichare scaly clay, mica schist, zeolitic rocks, and basaltic lava, respectively from
down- to up-stream. The zeolitic rock consist of celadonite-natrolite-palagonitemeta-basalt, zeolite
meta-calcareouspolymictic breccia, zeolite meta-pelite in which based on mineral geochemistry, these
rocks are metamorphosed under zeolite-facies (T= 120–220 °C and P= 1–5Kbar). While, mica schist
consists of garnet-muscovite-zoisite schist (meta-calcsilicate),garnet-tourmaline-muscovite schist,
andgarnet-muscovite greenschist (meta-pelite), as well as garnet-muscoviteortho-greenschist (metabasite) in which from pseudosection analysis, these areincluded intogreenschist-facies(T= 510–580 °C
and P= 0.74–1.08 Gpa). Furthermore, very low- to low-grade metamorphic rocks or metamorphosed to
un-metamorphosed rocks transitionsaredominantly composed by structural contact. Ortho-rock and
meta-peliteprotolith analysis show respectively MORB and island arc affinities before subducted and
cropped out in the accretionary wedgeby accretionary type exhumation. New discoveries about
Northern part of Luk Ulo Melange Complex from very low- to low-grade metamorphic
rockperspectives, hopefully can be used to complete the geological history in this area.
Keyword: zeolite-facies, greenschist-facies, very low- to low-grade metamorphism, Gebang
River
