ALBERT

Description: The Halmahera island belongs to the North Moluccas province (Maluku Utara), Indonesia. This K-shaped island is located in the eastern part of the Moluccas Sea, the only active arc-arc collision complex on the Earth. The western arm of the K forms a volcanic arc due to the former subduction of the Moluccas Sea plate underneath Halmahera. The region is characterized by intense seismic activity at crustal, intermediate depth, and along the subducting plate. At crustal level the Halmahera seismicity along the two eastern arms of the K show strike-slip faulting style. In November 2015 a localized intense and energetic seismic activity started around Jailolo volcano in the West Halmahera Regency. The seismic sequence intermittently lasted until February 2016 and hundreds of events were felt by the population and several buildings were destroyed and damaged by the shaking. The largest shocks of the sequence have been located by global seismicity networks (GEOFON and GCMT) showing normal faulting style. The temporal evolution of the seismicity seems to be more swarm-like type activity instead of mainshock-aftershock sequence. In spring 2016 a research project has been funded by the German's Humanitarian program in collaboration with BMKG, Indonesia, with the goal of understanding the origin of the intense seismic activity and the related hazard. In summer 2016 we instrumented the area with a dense seismic network composed of 29 short period and 6 broad-band seismometers. The instrument deployment aims at characterizing the seismicity of the Jailolo region in relationship with the 2015-2016 seismic activity. The network will help to understand the seismo-tectonic of the area and the relation between seismicity and the volcanic activity at Jailolo volcano and possible link with the 2015-2016 swarm. Should the seismic activity intensify as in November 2015, we can record it and narrow down the underlying physical mechanisms. Waveform data are available from the GEOFON data centre, under network code 7G, and are embargoed until the end of 2021.

Description: In the frame of the EU-project COSEISMIQ (COntrol SEISmicity and Manage Induced earthQuakes) natural and induced seismic events were monitored in Iceland. A temporary seismic network has been deployed in the Hengill geothermal region in Iceland, where the two largest geothermal power plants of the country are currently in operation. The GFZ contribution was the installation and operation of a small-scale seismic array in 2019-2021 in the vicinity of the broadband station MEI05 (ETH), in cooperation with ISOR (Iceland), ETH (Zurich) and DIAS (Dublin). This dataset is particularly valuable since a very dense network was deployed in a seismically active region where both induced and natural seismicity are occurring. For this reason, the collected COSEISMIQ-dataset can be used within a broad range of research topics in seismology ranging from the development and testing of new data analysis methods to induced seismicity and seismo-tectonics studies.

Description: Near Reykjavik/Iceland, a "soft stimulation” geothermal experiment was performed in the frame of the DESTRESS project in 2019. The installed seismic stations consist of short period, and borehole stations in and around Geldinganes, NE of Reykjavik. The task of this network is the monitoring of the seismic events in the area around the stimulation site. The installation started in late 2018 with 6 short period stations (Reykjavik Energy). Since July 2019 additional seismic stations were integrated as a small scale array on the island Geldinganes and additional short period stations. A borehole geophone chain was installed with 17 short period 3-component geophones with a vertical spacing of 10 meter in the depth interval 1040m to 1200 m. Waveform data are available from the GEOFON data centre, under network code YG, and are embargoed until January 2025.

Description: In January 2020, a swarm of earthquakes started under Thorbjorn volcano, Reykjanes, SW Iceland, associated to the uplift of up to 0.5 cm per day. Concern in Iceland is growing and the Iceland Meteorological Office suggested that possibly magma was intruded in the crust at shallow depth (3 to 9 km). The GFZ is starting a seismological Hazard and Risk Team (HART) in cooperation with IMO, ISOR and the University of Iceland Waveform data are available from the GEOFON data centre, under network code 9H, and are embargoed until January 2026.

Description: Following a sequence of seismic events detected by the National Geographic Institute (IGN Spain), on 13.09.2021 the new volcano Cumbre Vieja initiated an eruption, located on the mid-western flank at a location just to the north of the 1949 eruption site. The eruption fed a lava flow that buried already some hundreds of houses, with a high economic estimated loss. Previous studies have shown that La Palma was the source of 3 or 4 large sector collapses associated with avalanches under see and tsunami generation. This volcanic activity is accompanied with an increased seismic activity. The GFZ contributes to the monitoring of the seismic activity by sending experts in the frame of a Hazard and Risk Team (HART). Our partner is the National Geographic Institute. Besides tiltmeters, a temporary 4 station seismic network with TrilliumCompact 20 sec posthole seismometers, D-Cube digitisers (100 sample/sec) and C-Cubes LTE communication for real-time data transmission is being deployed near the Cumbre Vieja volcano, increasing the station density of the IGN network. Data access is being restricted for some time.

Description: This dataset contains processed (downsampled, rotated to local Äspö96 coordinate system, cut) broadband seismograms from two seismometers (Trillium Compact 120s), showing long-period transients on the horizontal components recorded during multiple hydraulic fracturing experiments in the Äspö Hard Rock Laboratory (HRL). Furthermore, the dataset contains extracted tilt time series and the injection parameters of the experiment to allow reproducing the results of Niemz et al. (2021). The seismic waveforms were recorded during meter-scale hydraulic fracturing experiments in the Äspö Hard Rock Laboratory (HRL) in Sweden (Zang et al., 2017). This dataset only contains a subset of the data recorded during the experiments, monitored by a complementary monitoring system. The two seismometers contained in this dataset (A89 and A8B) were located in galleries adjacent/close to the injection borehole (see Fig. 2 in Niemz et al., 2021). The experiments were conducted at the 410m-depth level of the Äspö HRL. Each of the six experiments (HF1 to HF6) consisted of multiple stages with an initial fracturing and three to five refracturing stages (see injection parameters contained in this dataset). The six injection intervals were located along a 28m-long injection borehole. The borehole was drilled sub-parallel to the minimum horizontal compressive stress direction. The distance of the two seismometers to the injection intervals in the injection borehole is between 17 m and 29 m for sensor A89 and 52 m to 72 m for sensor A8B. A89 and A8B correspond to BB1 and BB2 in Niemz et al., 2021. For more details regarding the experimental setup, see Zang et al., 2017; Niemz et al., 2020; and Niemz et al., 2021. The records of the two seismometers show long-period transients that correlate with the injection parameters. These transients are the response of the seismometers to a tilting of the gallery floor. The extracted tilt time series provide independent insight into the fracturing process during the hydraulic stimulations (Niemz et al., 2021).

Description: This data set contains measurements of an underground hydraulic fracture experiment at Äspö Hard Rock Laboratory in May and June 2015. The experiment tested various injection schemes for rock fracture stimulation and monitored the resulting seismicity. The primary purpose of the experiment is to identify injection schemes that provide rock fracturing while reducing seismicity or at least mitigate larger seismic events. In total, six tests with three different injection schemes were performed in various igneous rock types. Both the injection process and the accompanied seismicity were monitored. For injection monitoring, the water flow and pressure are provided and additional tests for rock permeability. The seismicity was monitored in both triggered and continuous mode during the tests by high-resolution acoustic emission sensors, accelerometers and broadband seismometers. Both waveform data and seismicity catalogs are provided.