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Map of Mt. Vesuvius with station positions (panel a) and hypocentral locations (panel b,c,d). Black triangles in the left-upper panel represent the digital portable stations. The white triangles show analogical permanent stations. OVO, the central station of the monitoring network, is marked with a black square.
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The Local-Magnitude scale actually in use at Vesuvius Observatory is basedon the measure of seismogram coda duration, and calibrated with data fromIrpinia aftershocks. A recent study on local seismic attenuation at Mt.Vesuvius reveals coda shapes highly different from those from Irpiniaaftershocks, and a very low quality factor, if compared to the...
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Context 1
... 1996, with M D in the range –0.4 to 3.2. The events have been located by using the P-wave onsets from all the available stations and S-wave onsets, when readable, from the 3-D stations. At the same site of BKE there is also a station of the permanent monitoring network. Figure 1 depicts an elevation contour map of Mt. Vesuvius together with station positions and epicentral locations. Location errors are within 500 m. Sample seismograms are shown in Figure 2. We measured the coda duration for a subset of 131 events belonging to the original set of 181 earthquakes, in order to check the routine operations performed by the analysts and to correct possible bias. Hence M D was calculated at OVO station using the ...
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... Wood-Anderson station located close to the city of Rome (Osservatorio di Monteporzio) (Del Pezzo et al., 1983). This task was performed several years ago for OVO station (the central station of the Vesuvius monitoring seismic network, see Figure 1). Obviously, as the station in Rome is about 200 km distant from OVO, the current Duration-Magnitude scale for OVO station results well calibrated for Magnitude greater than 3.5, the minimum Magnitude recorded by both stations. This scale was then used to calibrate the other stations of the permanent seismic network, and its extrapolation to Magnitudes lower than 3.5 is currently used to calculate the Magnitude of the low-energy quakes occurring at Mt. Vesuvius. So, due to this extrapolation, even though the duration Magnitude is considered sat- isfactory by most of seismological Observatories in the world (Eaton, 1992), it could be a biased estimate of the true values at V.O., especially for low values of the Magnitude. The best way to achieve an estimate as much as possible unbiased of the local Magnitude is to use the original Magnitude scale firstly developed by Richter, taking care in properly correcting for the real seismic attenuation in the area under investigation. An absolute local Magnitude scale obtained in this way allows also for an optimal comparison of the actual level of seismicity at Mt. Vesuvius with that measured on other active ...
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... main problem in performing this task is the evaluation of the attenuation curve for the maximum amplitudes in the wave-train. The source-station distance interval for most of the local volcano-tectonic earthquakes ranges from about 1 to 6 km (see Figure 1), with a pronounced gap from 6 to 30 km. Epicentral distances higher than 30 km are related to the tectonic seismicity of the Apennine chain (see also Figure 1 in Nostro et al., 1988), which is excluded from the present study. Due to this limited distance range, the experimental maximum amplitude decay with distance is difficult to fit to an empirical function, and this makes impossible to evaluate the attenuation law outside the area of the main volcanic complex, thus reducing the distance range of applicability of the Richter scale. The results from a recent study of local attenuation in the area of Mt. Vesuvius (Bianco et al., 1999) can be of some help in partly solving the above difficulty. We can in fact use the estimate of the inverse quality factor for S-waves, Q − 1 , in order to construct a ‘reasonable’ maximum amplitude distance attenuation curve. As the correction curve of the Richter formula is purely empirical, it is not parametrized as a function of the quality factor and of the coefficient of geometrical spreading. For this reason we use a technique similar to that proposed by Boore (1983), to simulate the propagation of a wave packet with the same characteristics of that composing the S-wave of microearthquakes, in a medium with the attenuation parameters equal to those measured for Mt. Vesuvius, and de- duce the maximum amplitude-decay curve for that medium. From this decay we estimate the curve of the maximum amplitude attenuation vs. distance. Wood- Anderson seismograms are calculated from real seismograms using convolution with the Wood-Anderson response. We performed the task in frequency domain using Fourier Transforms. Then the Wood-Anderson Magnitude is compared to the Duration-Magnitude scale in routine use at Vesuvius Observatory, and to the Moment-Magnitude scale (Lay and Wallace, 1995), which can be easily calculated once that attenuation coefficient for the spectral amplitude is known in the area. We show that below the level of Magnitude 1 the Duration-Magnitude scale does not well correlate with the other scales. Therefore some care is needed in interpreting the low-energy seismic release processes occurring at Mt. Vesuvius. The seismic monitoring network of Mt. Vesuvius is composed of 10 low-dynamic range (60 dB) stations telemetred to the Data Analysis Center (Centro di Sorveglianza) and 7 high-dynamic range (120 dB) temporary digital stations, with local recording. Sensors are 1 Hz Mark L4-C vertical component for the low-dynamic range stations and 1 Hz Mark L4-3D for the others, all set up at 70% of critical damping. Digital stations sample the seismic signals at 125 s.p.s. with a low-pass anti-alias filter at a cutoff frequency of 25 Hz. Response curves of the digital seismic stations were checked multiplying the complex transfer function of a damped forced harmonic oscillator to the complex transfer function of the anti-aliasing filter. The transduction level was estimated using the calibration coil of the MARK L4-3D seismometers. The procedure is summarized as follows: first, we put into the calibration coil a step current pulse, recording the corresponding output pulse in the time domain. Then we synthesized the theoretical output pulse as a function of G , the transduction constant and of h , the percent damping coefficient. The fit between experimental and theoretical pulse gives the proper parameters h and G . The resonance frequency of the sensors and the calibration coil motor constant were fixed at the values given by the manufacturer. Mt. Vesuvius seismicity has been characterized for the last 50 years by low Duration-Magnitude (up to M D = 3 . 4) earthquakes with an epicentral location close to the crater area and depths shallower than 6 km (Bianco et al., 1999). The Duration-Magnitude scale, M D , was obtained by Del Pezzo et al. (1983), who calibrated the scale to a reference Wood-Anderson seismometer located close to the city of Rome, using data from the 1980 Irpinia Earthquake aftershocks. Due to the high cultural noise level, originated by the position of Mt. Vesuvius located close to the city of Naples and its suburbs, many of the seismic recordings show a low signal to noise ratio. For the present analysis we used the recordings from the digital portable station BKE, one of the closest to the epicentral area, with the best signal to noise ratio and minimum site amplification. The data set we use in the present paper is the same as that used by Bianco et al. (1999) for a study on site- corrected seismic attenuation. It consists of 181 three component high-dynamical range recordings of local earthquakes which occurred in the period ...
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Citations
... The relative location of the sources and the recording sites did not allow for the calibration of earthquakes with a magnitude lower than 3.0; the regression was simply extrapolated to a lower magnitude [74], a procedure that could not ensure the correctness of the estimation at this range. As a matter of fact, Del Pezzo and Petrosino [89] demonstrated that this relation was not appropriate for smaller earthquakes. By using permanent and temporary stations, those authors derived the following relation: ...
... between the OVO duration magnitude and the BKE local magnitude, for 131 Vesuvius earthquakes, this showed that m d significantly underestimated m L at lower magnitudes ( Figure 16). According to this relation, the duration magnitude at OVO should be evaluated using [89]: ...
... We remark that the results obtained by [89] were well constrained, and were based (i) on the determination of an experimental distance-attenuation curve for Mt. Vesuvius events and (ii) on the simulation of Wood-Anderson seismograms, starting from recordings at a 1 Hz MARK L4-3D installed at BKE. ...
Here, we characterize the statistical behaviour of the Mt. Vesuvius seismicity using distinct available catalogues. Our analysis confirms that for this area, the GR distribution exhibited two scaling regimes of the b-value, not commonly observed for the standard frequency-magnitude distribution of earthquakes. By assuming a physical cause, we tested four different hypotheses for the source of the break in the scaling: finite size effect, depth variations in the b-value, radial dependence in the b-value, and different b-values for swarm and non-swarm events. None of the above reasons are able to explain the observation. Thus, we investigated the possibility of some pitfalls in magnitude estimation. Based on our analysis, we suggest there is a bias in the duration magnitude the catalogues are based on. This is due to the arbitrary extrapolation to smaller magnitudes of a linear regression derived for earthquakes with m≥3.0. When a suitable correction is applied to the estimated magnitude, the GR distribution assumes the usual shape, with a b-value closer to that usually observed in volcanic areas. Finally, the analysis of the time variation of some statistical parameters reveals that the state of the volcano appears to be stationary over the entire analysed period, possibly with only a slight decrease in the b-value, indicating a small reduction in differential stress.
... Specially calibrated relationships have been published for Hawaii, Vesuvius, Deception Island, Etna and Campi Flegrei (Z ú ˜ niga et al. 1988 ;Del Pezzo & Petrosino 2001 ;Havskov et al. 2003 ;Giampiccolo et al. 2007 ;Petrosino et al. 2008 ;Guardato et al. 2022 ). In this study, we aim to calculate the M W for Etna seismicity using the most suitable approaches to cover the characteristic magnitude range of Etna seismicity. ...
Accurate quantification of seismic activity in volcanic regions is an important asset for improving hazard and risk assessment. This is especially true for densely populated areas, as in the case of Etna volcano (Southern Italy). There, the volcanic hazard is amplified by the seismic risk of active faults, especially on the eastern flank of the volcano. In such a context, it is common to rely on moment magnitude (MW) to characterize seismicity and monitor the energy released during an eruption. In this study, we calculate the moment-based magnitude (MW) for selected seismic data sets, using different approaches in distinct magnitude ranges to cover the widest possible range of magnitude that characterizes Etna's seismicity. Specifically , we computed the MW from a data set of moment tensor solutions of earthquakes that occurred in the magnitude range 3.4 ≤ ML ≤ 4.8 during 2005-2020; we created a data set of seismic moment and associated MW for earthquakes 1.0 ≤ ML < 3.4 obtained by analysing source spectra; we fine-tuned two relationships, for shallow and deep earthquakes, to obtain MW from response spectra. Finally, we calibrated a specific relationship between MW and ML for the Etna area earthquakes in the range 1.0 ≤ ML ≤ 4.8. All the empirical relationships obtained in this study can be applied in real-time analysis of the seismicity to provide fast and robust information on the released seismic energy.
... Processing of these seismograms to ensure that they are directly comparable to more recent seismograms is not always straightforward, with scaling an issue in some spatio-temporal settings (e.g. Del Pezzo and Petrosino 2001;Ishii et al. 2015;Okal 2015). For example, the 1995 Ruapehu eruption was captured on both digital and visual records, this overlap allows comparisons to be made between triggered digital and processed RSAM/ SSAM vs continuous visual (paper seismogram) records. ...
There are currently no quantitative short-term eruption forecasts based on peer-reviewed and validated models that are operational for New Zealand’s volcanoes. Specific forecasts produced for work-risk assessments are not generally publicised. During a volcanic crisis, eruption forecasts are demanded under high stress and time-restricted conditions. Many forecasting options exist but none are proven as universally viable, with testing and calibration limited to the hindcasting of specific events. Here, we compare the requirements of six methods with currently available data and monitoring capabilities at each of New Zealand’s volcanoes to determine which methods are currently feasible, as well as those options that may be implemented with additional effort or equipment. In New Zealand, the major limiting factor in method selection is the low number of past instrumentally monitored eruptions. This data gap may be filled by carefully selected analogue data from a global volcano set and expert knowledge. Event trees and the failure forecasting method may be set up at most volcanoes with minimal effort, but the latter can only forecast eruption onset time. Expert interpretation is the only method available in New Zealand for any forecast output type.
... The stations of the network record velocity waveforms, but the M L is defined for displacement waveforms on a Wood-Anderson seismometer. Therefore, the seismogram undergoes pre-processing prior to the linear least-squares inversion: the velocity seismogram is integrated to ground motion, the instrument response is removed, a Wood-Anderson instrument response is applied (e.g., Butcher et al. 2017;Bormann et al. 2013;Del Pezzo and Petrosino 2001;and Hutton and Boore 1987), and finally, the waveform is filtered between 2 and 20 Hz. From each pre-processed waveform, the value for A is one-half of the peak-to-peak amplitude of the largest S-wave on the vertical component. ...
In August 2010, Sinabung volcano began erupting after more than a thousand years of dormancy. Following several weeks of phreatic eruptions, the eruptions ceased and Sinabung entered what became an inter-eruptive period of dominantly seismic unrest. While standard equations for understanding the size of an earthquake (local magnitude (ML), coda magnitude (MC), and seismic energy release (ER)) have long been developed, it is best practice to fine tune these relations for a given region and period of study to more accurately describe seismicity and to directly compare it with other volcanic systems. More accurate descriptions of magnitudes and energy release are vital to accurate volcanic eruption forecasting and evaluation of seismic and volcanic risk. In this study, we use high-frequency volcano-tectonic (VT) earthquakes recorded on a temporary three-component network installed between October 2010 and December 2011 in the region around Sinabung volcano to better constrain the seismic parameters of and better understand this previously unstudied volcano. We determine region-specific formulas for ML, MC, and ER as follows:$$ {\mathrm{M}}_{\mathrm{L}}={\log}_{10}A+1.1252{\log}_{10}r+0.0280\ r-2.5427,\kern0.5em {\mathrm{M}}_{\mathrm{C}}=0.7764\ {\log}_{10}{t}_{coda}+0.0676\ r-0.7185,\kern0.5em \mathrm{and}\kern0.5em {\log}_{10}\left({\mathrm{E}}_{\mathrm{R}}\right)=1.5720{\mathrm{M}}_{\mathrm{L}}+11.5258, $$where A, r, and tcoda are maximum amplitude on a Wood-Anderson seismogram, hypocentral distance (km), and the coda duration (s), respectively. Constants in the ML equation have physically interpretable meanings. The constant for the geometrical spreading term (log10r term) equals one for perfect spherical spreading of the waveform. Our value is greater than one and thus suggests that wavefronts spread at a slightly different rate than for simple spherical spreading. The constant for the attenuation term (r term) is consistent with locally mapped attenuative deposits (limestones and tuffs) and previous 3D tomographic results. Our MC equation differs from a previous study, likely because different data in a different time period were used. Earthquake hypocenters are consistent with those located in previous tomographic studies, and we interpret the earthquakes in this study as distal VT earthquakes induced by continued magmatic intrusion at Sinabung over the period of October 2010–December 2011.
... The stations of the network record velocity waveforms, but the M L is defined for displacement waveforms on a Wood-Anderson seismometer. Therefore, the seismogram undergoes pre-processing prior to the linear least-squares inversion: the velocity seismogram is integrated to ground motion, the instrument response is removed, a Wood-Anderson instrument response is applied (e.g., Butcher et al. 2017;Bormann et al. 2013;Del Pezzo and Petrosino 2001;and Hutton and Boore 1987), and finally, the waveform is filtered between 2 and 20 Hz. From each pre-processed waveform, the value for A is one-half of the peak-to-peak amplitude of the largest S-wave on the vertical component. ...
In August 2010, Sinabung volcano began erupting after more than a thousand years of dormancy. Following several weeks of phreatic eruptions, the eruptions ceased and Sinabung entered what became an inter-eruptive period of dominantly seismic unrest. While standard equations for understanding the size of an earthquake (local magnitude (M L), coda magnitude (M C), and seismic energy release (E R)) have long been developed, it is best practice to fine tune these relations for a given region and period of study to more accurately describe seismicity and to directly compare it with other volcanic systems. More accurate descriptions of magnitudes and energy release are vital to accurate volcanic eruption forecasting and evaluation of seismic and volcanic risk. In this study, we use high-frequency volcano-tectonic (VT) earthquakes recorded on a temporary three-component network installed between October 2010 and December 2011 in the region around Sinabung volcano to better constrain the seismic parameters of and better understand this previously unstudied volcano. We determine region-specific formulas for M L , M C , and E R as follows: M L ¼ log 10 A þ 1:1252log 10 r þ 0:0280 r−2:5427; M C ¼ 0:7764 log 10 t coda þ 0:0676 r−0:7185; and log 10 E R ð Þ ¼ 1:5720M L þ 11:5258; where A, r, and t coda are maximum amplitude on a Wood-Anderson seismogram, hypocentral distance (km), and the coda duration (s), respectively. Constants in the M L equation have physically interpretable meanings. The constant for the geometrical spreading term (log 10 r term) equals one for perfect spherical spreading of the waveform. Our value is greater than one and thus suggests that wavefronts spread at a slightly different rate than for simple spherical spreading. The constant for the attenuation term (r term) is consistent with locally mapped attenuative deposits (limestones and tuffs) and previous 3D tomographic results. Our M C equation differs from a previous study, likely because different data in a different time period were used. Earthquake hypocenters are consistent with those located in previous tomographic studies, and we interpret the earthquakes in this study as distal VT earthquakes induced by continued magmatic intrusion at Sinabung over the period of
... In volcanic areas the calculation of the local magnitude M L is more objective than that of M D because the measurement of the signal amplitude is less ambiguous with respect to the decay of the earthquake coda, which may be masked by the presence of noise, volcanic tremor, or other shocks [Del Pezzo and Petrosino, 2001;D'Amico and Maiolino, 2005]. Therefore, since magnitude estimation in M D and M L , although mutually related, do not produce the same results, it is mandatory to adopt an empirical conversion to produce a homogeneous catalogue for Mt. ...
... The advantage of the above method is that the duration, defined as the time interval between the onset of the first pulse and the time when the amplitude of the seismogram coda decreases below the noise level, is influenced minimally by inaccuracies in the instrumental response function and the hypocentral location [Gasperini et al. 2013]. However, in volcanic areas the decay of the earthquake coda may be masked by the presence of noise, volcanic tremor or other shocks [Del Pezzo andPetrosino 2001, D'Amico andMaiolino 2005], so that calculation of the local magnitude, based on the less ambiguous signal amplitude, is desirable to estimate magnitude properly. ...
A homogenous database of magnitude observations is a basic requirement for seismic hazard estimation and other seismic studies. Unfortunately, the magnitude reported in the seismic catalogue of Mt. Etna is not homogenous. Until 2005 only the duration magnitude (MD) is available, though since then the more stable local magnitude (ML) has also been calculated. To overcome this limitation, earthquake data recorded at Mt. Etna during the period 2005 – 2014 were used to derive a new relationship between local and duration magnitude, by applying the General Orthogonal Regression (GOR) which is an alternative to least squares when the ratio between errors on the independent and the dependent variables can be estimated. The relationship obtained is:
ML = 1.164 (± 0.011) * MD - 0.337 (± 0.020)
The new relationship allows to back-extend the local magnitude dataset to cover a period of about 15 years.
... In volcanic areas the calculation of the local magnitude M L is more objective than that of M D because the measurement of the signal amplitude is less ambiguous with respect to the decay of the earthquake coda, which may be masked by the presence of noise, volcanic tremor, or other shocks [Del Pezzo and Petrosino, 2001;D'Amico and Maiolino, 2005]. Therefore, since magnitude estimation in M D and M L , although mutually related, do not produce the same results, it is mandatory to adopt an empirical conversion to produce a homogeneous catalogue for Mt. ...
... In volcanic areas the calculation of the local magnitude M L is more objective than that of M D because the measurement of the signal amplitude is less ambiguous with respect to the decay of the earthquake coda, which may be masked by the presence of noise, volcanic tremor, or other shocks [Del Pezzo and Petrosino, 2001;D'Amico and Maiolino, 2005]. Therefore, since magnitude estimation in M D and M L , although mutually related, do not produce the same results, it is mandatory to adopt an empirical conversion to produce a homogeneous catalogue for Mt. ...
The marine sector of the Campi Flegrei caldera has started to be monitored over the long-term with a
seafloor equipment deployed in the Gulf of Pozzuoli from 2008. The equipment includes a set of
geophysical, oceanographic and environmental sensors integrated in a marine platform that was specifically
designed for real-time monitoring. This platform, named CUMAS (Cabled Underwater Multidisciplinary
Acquisition System), was installed in the center of the Gulf at about 2.5 km south of Pozzuoli where the sea
depth is about 100 m [Iannaccone et al., 2010]. The CUMAS system consists of a seafloor module connected
by cable to a buoy (elastic beacon type) equipped with autonomous power supply systems, real-time datatransmission
devices and a weather station. The core of CUMAS is the seafloor module that contains
geophysical and oceanographic sensors, in particular, a three-component broadband seismometer, a best in
class three axis MEMS accelerometer, a low-frequency hydrophone and a high-resolution sea bottom
pressure recorder. A single-point acoustic, three-component, water-current meter and a water-temperature
sensor were also installed to monitor some water local physical parameters. A set of status sensors, which
also included a digital compass and a two-component digital tilt-meter, were added to track the attitude of
the module over the course of the experiment. The marine monitoring system transmits the data in real-time
and is integrated into the Monitoring Center in Naples managed by INGV-Osservatorio Vesuviano.
A continuous GPS station has been installed since the end of 2011 on the top of the buoy. The elastic
beacon buoy forms a structure which is rigidly connected by a mechanical cable to the ballast on the sea
bottom, a submerged float at the base of the buoy maintains tension on the cable and ensure the overall
buoyancy of the system. In this way, any vertical movement of the seafloor propagates rigidly to the emerged
part of the buoy itself, allowing measurement of the vertical movement of the sea floor by the GPS station.
The analysis of about 17 months of continuous GPS data, from January 2012 to May 2013, revealed an
overall uplift of about 3-4 cm allowing a first measurement of vertical seafloor displacement in the Campi
Flegrei caldera [De Martino et al., 2014].
A new opportunity to enhance the deployed system was given by a national project, EMSO-MedIT,
which is providing the necessary resources to expand the data acquisition to other areas of the Gulf of
Pozzuoli. New improved systems similar to CUMAS are going to be deployed in three additional marine
sites of the Gulf of Pozzuoli and the existing tide gauges network will be renewed with state-of-art sensors.
The overall new monitoring infrastructure will allow to extensively map the seafloor vertical displacement
and to improve the interpretative models of the bradyseism phenomenon including a more accurate location
of earthquakes in the marine areas and extending to lower magnitude values the detection of the seismic
activity.
... Since 2000, thanks to the installation of digital seismograph stations in Italy (Amato and Mele 2008) , magnitudes have been estimated by local magnitude M L (Richter 1935), obtained by synthetic Wood-Anderson seismograms taking into account the maximum peak-to-peak amplitude of the signal and the epicentral distance (Gasperini 2002). The procedure consists of correcting the seismic signals for the complex instrument transfer function and then applying the complex Wood-Anderson transfer function (e.g., Del Pezzo and Petrosino 2001; D'Amico and Maiolino 2005 ). The calculation of M L is more objective than that of M D because the measurement of the signal amplitude is less ambiguous with respect to the decay of the earthquake coda, which may be masked by the presence of noise, volcanic tremor, or other shocks. ...
The historical activity of Mt. Etna is well documented by a large amount of sources that have reported the seismic and volcanic phenomena occurring on the volcano since the late 1600s (Azzaro et al. 2000; Branca and Del Carlo 2005). Such a large dataset of historical information is not common and is comparable, in Italy, to that of Vesuvius (Giudicepietro et al. 2010). As for long-term seismicity known through macroseismic data, the first release of the historical catalog of Mt. Etna earthquakes from 1832 to 1998 was published ten years ago (hereinafter CMTE catalog) and since then has been regularly updated (CMTE Working Group 2008). With 1,790 earthquakes listed, the CMTE catalog provides an overall picture of the space-time evolution of the major seismicity and possible relationships with past eruptive activity ( e.g. , Azzaro and Barbano 1996; Azzaro et al. 2001). On the other hand, it was only in 1967 that the first seismograph station was installed at Etna. A complete seismograph network began to operate in the early 1980s with nine short-period analog stations, evolving in the last decade into a broadband digital seismograph network consisting of some 30 stations (Patane et al. 2004). For a long time, this network has operated without uniform coverage of the volcano, since it was largely aimed at monitoring eruptive activity in the middle-upper parts of Etna; such a situation has meant favoring the macroseismic approach in studying the severely damaging earthquakes that struck the populated slopes of the volcano. As a consequence, this typology of data has been used for defining the seismotectonic features (Azzaro 2004) and seismic hazard of this area (Azzaro et al. 2008).
In the seismic catalogs the estimation of magnitude for earthquakes occurring in the pre-instrumental period is obtained through empirical relationships using the value …
