![]() The preamp's MM phono-input boards were rebuilt ($195) and fitted with Vishay Z Foil loading resistors that had also been given the Deep Cryo chill ($125). ![]() (AV Options is also an authorized Naim Audio service center and has expanded into retailing, via internet, a few products that fit their Naim-friendly view of the hi-fi world.) The NAC 32-5 was given the basic AVO rebuild service for that model, includ- ing upgraded locking DIN sockets from PrehKeyTec of Germany ($995) and WBT Nexgen RCA jacks, treated with AVO's "Deep-Cryo" cryogenic treatment ($180), in place of the original BNC Phono-1 sockets. (In 1988, my own Naim setup was humbler: I started out with the less expensive NAC 62 preamp and NAP 140 amp, later upgrading to a Naim-reconditioned secondhand NAP 250.)Īs with the Nait 2 integrated amp I wrote about in the May 2016 Stereophile, the Naim components in question had been serviced by AV Options (footnote 3), a US company whose star technician is UK-born Chris West, who worked for Naim for a goodly number of years. In 1988, the 32-5/250/Hi-Cap combination was Naim's second-best amplification system, bettered only by the use of two NAP 135 monoblocks in place of the stereo amp. The presence of a larger volcanic system in the eastern IFM could influence magmatism and account for the multiple closely spaced volcanic centers in this region.The Naim components in question were their NAC 32-5 preamplifier and NAP 250 power amplifier, supplemented with their Hi-Cap outboard power supply that last item was devised as an upgrade to a more basic system in which DC from the Naim amp's own power supply is used to power the preamp. These observations, combined with observations of vent orientation and morphology and gas flux, suggest the area between Cleveland and Tana represents a zone of complicated volcano-tectonic interaction, similar to calderas elsewhere in the Aleutian arc. These earthquakes have vertically-oriented P-axes and a greater percentage occur in families. VT hypocenters also extend ~7 km northeast of Cleveland's summit at depths of 5 to 10 km BSL, under a group of Holocene-aged vents between Mount Cleveland and Tana. The time-history of VT earthquakes and shallow LP events suggest their occurrence may track the transfer of magma and fluids from the mid-crust to the shallow portions of the conduit system and may provide a means to anticipate future explosions and periods of dome growth. These observations, and a relatively slow one-dimensional seismic velocity model, are consistent with a shallow body of magma that is fed through a deeper conduit system. VT focal mechanisms have horizontal P-axes that align with the regional axis of maximum stress. VT earthquakes beneath Mount Cleveland occur at depths of 2 to 8 km below sea level (BSL) and range in magnitude from −0.2 to 1.8. LP events appear to cluster at shallow depth beneath the active crater of Mount Cleveland and almost all of the explosions occur without identifiable short-term (hours to days) seismic precursors. This analysis reveals the full range of seismic event types expected in a highly active volcanic environment and includes Volcano-Tectonic (VT) earthquakes, Long-Period (LP) events, and explosion signals. We characterize seismicity beneath Chuginadak Island through automated analysis of event waveform frequency content, development of a one-dimensional P-wave velocity model, calculation of earthquake hypocenters, magnitudes, focal mechanisms, and identification of earthquake families. During the study period (July 2014–January 2019), eruptive activity at Cleveland was characterized by small explosions separated by periods of lava effusion that formed small domes in the volcano's summit crater. Collectively, these stations provided the first seismic observations of this frequently active volcano and the surrounding Holocene-aged volcanic vents. The Alaska Volcano Observatory (AVO) installed two permanent broadband seismometers on Chuginadak Island in 2014, and we operated a temporary broadband network focused on the western side of the island in 2015–2016. ![]() The persistently active Mount Cleveland volcano, on the western side of Chuginadak Island, is surrounded by several closely spaced Quaternary volcanic centers including Carlisle, Herbert, Kagamil, Tana, and Uliaga, and numerous small satellite vents on Chiginadak between Cleveland and Tana. Cleveland and Tana are remote volcanoes located in the central Aleutian volcanic arc on the eastern end of the Islands of Four Mountains (IFM).
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