The March 11th, 1978 Ferruzzano earthquake is the most recent moderate-to-major earthquake occurred in the southern Calabrian region (southern Italy), one among the highest seismic risk areas of the whole Mediterranean. Previous information available from the literature on the 1978 earthquake is quite contrasting and not well framed in the regional seismotectonic scenario. In the present study we selected and digitized analog seismograms coming from stations of the Euro-Mediterranean region to invert for the deviatoric seismic moment tensor through a time-domain algorithm properly implemented to analyze data recorded before the advent of the digital era. Moreover, we estimated a new hypocentral location by using original bulletin data and a non-linear probabilistic earthquake location technique working with 3D velocity models. The quality and stability of the obtained results, both for hypocenter location and moment tensor inversion, were accurately checked by several inversion tests. Our results indicate that the 1978 earthquake (i) occurred westward and at a shallower depth respect to previous hypocenter locations, (ii) is characterized by a ca. N-S trending normal faulting mechanism and (iii) has a moment magnitude of 4.7, thus suggesting an overestimate of previous evaluations. This study furnishes new information on the 1978 Ferruzzano earthquake allowing to better frame it in the regional seismotectonic scenario and also proves that the time-domain waveform inversion algorithm applied to digitized old seismograms is capable to successfully invert also Mw < 5 earthquakes. The obtained results pave the way for future analyses of the early instrumental seismicity potentially capable to furnish new constraints to local and regional seismotectonic modeling.

Spectral analysis of earthquake recordings provides fundamental seismological

information. It is used for magnitude calculation, estimation of attenuation, and

the determination of fault rupture properties including slip area, stress drop, and radiated

energy. Further applications are found in site-effect studies and for the calibration

of simulation and empirically based ground-motion prediction equations.

We identified two main limitations of the spectral fitting methods currently used in

the literature. First, the frequency-dependent noise level is not properly accounted for.

Second, there are no mathematically defensible techniques to fit a parametric spectrum

to a seismogram with gaps.

When analyzing an earthquake recording, it is well known that the noise level is not

the same at different frequencies, that is, the noise spectrum is colored. The different,

frequency-dependent, noise levels are mainly due to ambient noise and sensor noise.

Methods in the literature do not properly account for the presence of colored noise.

Seismograms with gaps are usually discarded due to the lack of methodologies to

use them. Modern digital seismograms are occasionally clipped at the arrival of the

strongest ground motion. This is also critical in the study of historical earthquakes in

which few seismograms are available and gaps are common, significantly decreasing

the number of useful records.

In this work, we propose a method to overcome these two limitations. We show

that the spectral fitting can be greatly improved and earthquakes with extremely low

signal-to-noise ratio can be fitted. We show that the impact of gaps on the estimated

parameters is minor when a small fraction of the total energy is missing. We also

present a strategy to reconstruct the missing portion of the seismogram.

On 21 August 1962 an earthquake sequence set off near the city of Benevento, in Italy's southern Apennines.

Three earthquakes, the largest having Mw 6.1, struck virtually the same area in less than 40 min (at 18:09, 18:19 and 18:44 UTC, respectively). Several historical earthquakes hit this region, and its seismic hazard is accordingly among the highest countrywide. Although poorly understood in the past, the seismotectonics of this region can be revealed by the 1962 sequence, being the only significant earthquake in the area forwhichmodern seismograms are available.

We determine location, magnitude, and nodal planes of the first event (18:09 UTC) of the sequence. The focal mechanismexhibits dominant strike-slip rupture along a north-dipping, E-W striking plane or along a west-dipping, N-S striking plane. Either of these solutions is significantly different fromthe kinematics of the typical large earthquakes occurring along the crest of the Southern Apennines, such as the 23 November 1980 Irpinia earthquake (Mw 6.9), caused by predominant normal faulting along NW-SE-striking planes.

The epicentre of the 21 August 1962, 18:09 event is located immediately east of the chain axis, near one of the three north-dipping, E-W striking oblique-slip sources thought to have caused one of the three main events of the December1456 sequence (Io XIMCS), the most destructive events in the southern Apennines known to date.

Wemaintain that the 21August 1962, 18:09 earthquake occurred along the E-Wstriking fault systemresponsible for the southernmost event of the 1456 sequence and for two smaller but instrumentally documented events that occurred on 6May 1971 (Mw 5.0) and 27 September 2012(Mw 4.6), further suggesting that normal faulting is not the dominant tectonic style in this portion of the Italian peninsula.

This article corrects: F. Bernardi, M.G. Ciaccio, B. Palombo and G. Ferrari, Moment tensor inversion of early instrumental data: application to the 1917 High Tiber Valley, Monterchi earthquake, Annals of Geophysics, 59 (3), 2016, S0318; doi:10.4401/ag-6850.

In this paper we present a new study on the High Tiber Valley earthquake occurred on April 26, 1917. Using the digitized data from mechanical seismograph records, we computed the source parameters like focal mechanism and moment magnitude from moment tensor (MT). The study of historical earthquakes from an instrumental perspective is crucial because of the complexity of problems associated with the study of seismograms of moderate to large earthquakes occurred from the late 19th century until the early 1960s. Since historical earthquake records show significant uncertainties in phase arrival times and have been recorded by seismograph generally with short natural period, we developed a code to compute the MT based on a forward modeling technique, which uses the amplitude spectra of the full waveform length and the first P-arrival polarities to constrain the P- and T-axes. The best solution is determined by the best fit between the observed and synthetic amplitude spectra and from the coherency between the observed and the theoretical first P-arrival polarities.

The 1917 High Tiber Valley earthquake is one of the most important 20th century earthquake occurred in the Italian Peninsula for which the focal mechanism and moment magnitude from seismic records are not available. Additionally, we apply a multidisciplinary approach to characterize the source of this earthquake, combining instrumental, macroseismic, geological and tectonic data and investigations. The computed MT results in a north-south normal fault mechanism (strike: 147°, dip: 29°, slip: −94°), which is consistent with the strike estimated from the macroseismic data (157°). The moment magnitude calculated from the MT and that derived from the macroseismic data are Mw=5.5±0.2 and Mw=5.9±0.1, respectively.

On 30 October 1930, anMw 5.8 earthquake hit the northern Marche coastal area (central Italy), causing significant damage (I0 VIII–IX degree Mercalli–Cancani– Sieberg) along a 40 km stretch of the Adriatic coast between Pesaro and Ancona, centered on the town of Senigallia. This area is characterized by relatively infrequent and moderate-sized earthquakes and by elusive active faults. In spite of the presence of wellknown northwest–southeast-trending, northeast-verging fault-propagation folds forming the outer thrusts of the Apennines, the current level of activity, and the kinematics of these coastal structures are still controversial.

We present a multidisciplinary analysis of the source of the 30 October 1930 Senigallia earthquake, combining instrumental and macroseismic data and elaborations with available evidence from geological and tectonic investigations.We determine the main seismic parameters of the source, including the earthquake location, its magnitude, and, for the first time, its focal mechanism, providing the first instrumental evidence for thrust faulting along the northern Marche coastal belt.

Our findings provide conclusive evidence for the current activity of the northern Marche coastal thrusts. As such they have significant implications for the seismic hazard of the area, a densely populated region that hosts historical heritage, tourism facilities, industrial districts, and key transportation infrastructures.

Online Material: Description of method used for moment tensor computation, tables of focal mechanisms and recording stations, and figures of seismic flux and uncertainty maps for macroseismic epicenters.

Foreword

Seismograms are the most comprehensive and quantitative documents of ground motion produced by earthquakes . First preserved records account for more than 100 years of instrumental seismology already, outperforming the time-span covered by modem broad-band seismic networks. But their uniqueness, as a document, prior to the generalization of massive methods of copy and distribution, limits the usability and availability of the earliest seismograms for research purposes. Contemporaneous analysis of old seismograms predated fundamental developments in quantitative seismology, as well as the digital revolution, suggesting the reanalysis of these unique and valuable records with modem seismological tools for the direct calculation of earthquake source parameters, at least for the most relevant events.

However, this is not straightforward: Early seismograms have been recorded at instruments with low dynamic range and narrow frequency band. Many times the complementary information required to process the records and to recover ground displacement, like instrument calibration and time accuracy, has been lost or is doubtful. In fact, procedures to make old seismograms useful for quantitative analysis are, in many aspects, similar to those needed to process and to use old macroseismic information. The present contribution reviews the main topics and methodologies leading to a proper use of old seismograms and related documents, including the location and distribution of the original seismograms and recording system information, as well as the sequence from the original paper seismogram to digital ground displacement, involving digitization, trace correction and deconvolution of the instrument response. We discuss the potential and the limitations of such treatments, and review some applications of recovered records in retrieving earthquake source parameters through full waveform analysis.  

The Southern Apennines chain is related to the west-dipping subduction of the Apulian lithosphere. The strongest seismic events mostly occurred in correspondence of the chain axis along normal NW–SE striking faults parallel to the chain axis. These structures are related to mantle wedge upwelling beneath the chain. In the foreland, faulting develops along E–W strike-slip to oblique-slip faults related to the roll-back of the foreland. Similarly to other historical events in Southern Apennines, the I0 = XI (MCS intensity scale) 23 July 1930 earthquake occurred between the chain axis and the thrust front without surface faulting. This event produced more than 1400 casualties and extensive damage elongated approximately E-W. The analysis of the historical waveforms provides the chance to study the fault geometry of this ‘‘anomalous’’ event and allow us to clarify its geodynamic significance. Our results indicate that the MS = 6.6 1930 event nucleated at 14.6 ± 3.06 km depth and ruptured a north dipping, N100_E striking plane with an oblique motion. The fault propagated along the fault strike 32 km to the east at about 2 km/s. The eastern fault tip is located in proximity of the Vulture volcano. The 1930 hypocenter, similarly to the 1990 (MW = 5.8) Southern Apennines event, is within the Mesozoic carbonates of the Apulian foredeep and the rupture developed along a ‘‘blind’’ fault. The 1930 fault kinematics significantly differs from that typical of large Southern Apennines earthquakes, which occur in a distinct seismotectonic domain on late Pleistocene to Holocene outcropping faults.

These results stress the role played by pre-existing, ‘‘blind’’ faults in the Apennines subduction setting.

Abstract

We collected analog seismogram recordings and seismic bulletins for two moderate magnitude earthquakes in the province of Jaén, southern Spaio, on 10 March and 19 May 1951, and the series of aftershocks. Seismograms from the two main events reveal striking similarity, pointing to nearby locations and similar source mechanisms. This casts a shadow on the quality of preserved phase readings and macroseismic data, which suggests a distance of several tens of kilometers between both mainshocks and aftershocks. A critica! review of available phase readings permitted usto detect severa! misinterpretations in the originai bulletins and to obtain better constrained hypocenter relocations-about 10 km apart-for the two mainshocks, as well as location estimates for 20 aftershocks. The recording of the 1951 Jaén earthquake doublet at a network of common stations allows a straightforward quality control of our digitized seismograms by waveform comparison . We estimate faulting parameters of the two mainshocks from regional moment tensor inversion, obtaining moment magnitude Mw 5.2 and M w 5.3, respectively, depth of 20 km, and strike-slip faulting mechanisms with minor normal slip component and northeast-southwest oriented T axes. Deconvolution of body waveforms from an Mw 4.4 aftershock yields simple triangolar source time functions for both main events, with durations close to 1 sec. While severa! previous studies had difficulties in characterizing these earthquakes, partially describing them as unusual intermediate deep focus events, we propose simple shear faulting sources in the middle crust and faulting geometries consistent with the regional seismotectonic framework.  

We collected analog seismogram recordings and seismic bulletins for two moderate magnitude earthquakes in the province of Jaén, southern Spain, on 10 March and 19 May 1951, and the series of aftershocks. Seismograms from the two main events reveal striking similarity, pointing to nearby locations and similar source mechanisms. This casts a shadow on the quality of preserved phase readings and macroseismic data, which suggests a distance of several tens of kilometers between both mainshocks and aftershocks. A critical review of available phase readings permitted us to detect several misinterpretations in the original bulletins and to obtain better constrained hypocenter relocations—about 10 km apart—for the two mainshocks, as well as location estimates for 20 aftershocks. The recording of the 1951 Jaén earthquake doublet at a network of common stations allows a straightforward quality control of our digitized seismograms by waveform comparison. We estimate faulting parameters of the two mainshocks from regional moment tensor inversion, obtaining moment magnitude Mw 5:2 and Mw 5:3, respectively, depth of 20 km, and strike-slip faulting mechanisms with minor normal slip component and northeast– southwest oriented T axes. Deconvolution of body waveforms from an Mw 4:4 aftershock yields simple triangular source time functions for both main events, with durations close to 1 sec. While several previous studies had difficulties in characterizing these earthquakes, partially describing them as unusual intermediate deep focus events, we propose simple shear faulting sources in the middle crust and faulting geometries consistent with the regional seismotectonic framework.

Online Material: Phase arrival times, seismograph constants for deconvolution, and color plots of probability density functions.

Content

PART ONE................................................................................................................................................................... 2

Agamennone, Giovanni (Rieti, 1858 June 24 . Rome, 1949 October 3).................................................................. 2

Alfano, Giovan Battista (Naples, 1878 December 8 . 1955 December 27).............................................................. 3

Baratta, Mario (Voghera, 1868 August 13 . Casteggio, 1935 September 4)............................................................ 3

Bertelli, Timoteo (Bologna,1826 October 26 . Florence, 1905 February 6) ............................................................ 4

Bina, Andrea (Milan 1724 January 1 . Milan 1792 March 8) .................................................................................. 7

Cacciatore, Niccolò (Casteltermini, 1780 January 26 . Palermo, January 1841 January 28)................................... 7

Caloi, Pietro (Monforte d.Alpone (VR) 1907 February 22 . Rome 1978 February 13)........................................... 8

Cancani, Adolfo (Rome, 1856 February 18 . Rome, 1904 May 28) ........................................................................ 9

Cavalleri, Giovanni Maria (Crema 1807 November 18 . Monza 1874 December 1)............................................. 10

Cavalli, Atanasio (Asti c.1717 . Rome? c.1798) .................................................................................................... 11

Cecchi, Filippo (Ponte Buggianese, 1822 May 31 . Florence, 1887 May 1).......................................................... 12

De Rossi, Michele Stefano (Rome, 1834 October 30 . Rocca di Papa, on 1898 October 23)................................ 13

Grablovitz, Giulio (Trieste, 1846 . Casamicciola, 1928 September 19) ................................................................ 16

Guzzanti, Corrado (Mineo, 1852 June 2 . Mineo, 1934 March 19) ....................................................................... 18

Mercalli, Giuseppe (Milan, 1850 May 21 . Naples, 1914 March 19)..................................................................... 20

Oddone, Emilio (Baldissero Canavese, 1864 October 28 . Torrespaccata, 1940 August 26) ................................ 22

Palmieri, Luigi (Faicchio, 1807 April 21. Naples, 1896 September 9).................................................................. 23

Serpieri, Alessandro (born in San Giovanni a Marignano, 1823 October 31 . Fiesole, 1885 February 2) ............. 25

Tacchini, Pietro (Modena, 1838 March 21 - Spilamberto (Modena), 1905 March 24)........................................... 26

Taramelli, Torquato (Bergamo, 1845 October 15 . Pavia, 1922 March 31)........................................................... 27

Vicentini, Giuseppe (Ala, 1860 November 2 - Ala, 1944 November 15) ............................................................... 29

PART TWO................................................................................................................................................................ 31

Alfani, Guido (Florence, 1876 January 17 . Florence, 1940 November 20) .......................................................... 31

Cirillo, Nicola (Grumo Nevano, 1671 September 10 .Naples, 1735 July 2).......................................................... 33

Girlanda Antonino (Laureana di Borrello, 1913 August 28 . Messina, July 1988 July 13) ................................... 35

Galli, Ignazio (Velletri, 1841 July 20 . Rome, 1920 February 10)......................................................................... 35

Goiran, Agostino (Nice, 1835 . Nice, 1909) .......................................................................................................... 36

Palazzo, Luigi (Turin, 1861 January 18 . Florence, 1933 June, 13)....................................................................... 38

Riccò, Annibale (Modena, 1844 September 14 . Rome, 1919 September 23)....................................................... 38

Silvestri, Orazio (Florence, 1835 . Catania, 1890 August 17) ............................................................................... 39

Valle, Paolo Emilio (Rome, 1913 January 6 . Rome, 1970 November 15)............................................................ 40

PART THREE ............................................................................................................................................................ 42

Somigliana, Carlo (Corno, 20th September 1860 . Casanova Lanza, on 20th June 1955)....................................... 42

A moment tensor solution is derived for the great 1938 Banda Sea earthquake, one of the largest events for which no definitive focal geometry has been published. We apply the method of preliminary determination of focal mechanism, which consists of inverting for a moment tensor using exclusively the spectral amplitudes of mantle Rayleigh and Love waves, while discarding the phase information which can be affected by uncertainties in relative timing between historical records. From a dataset of 17 records at seven stations, we obtain a robust solution, featuring a very large moment of 8.37U1028 dyn-cm, the centroid depth being constrained around 60 km by minimizing the rms residual of the inversion. The method involves an inherent two-fold 180‡ indeterminacy on the orientations of strike and slip, which is lifted by the examination of the polarization of long-period body waves read individually on original records, resulting in a mostly thrust-faulting mechanism (strike: 276‡; dip: 63‡; slip : 70‡).

This approach, coupled with more traditional relocation efforts, allows a rare glimpse of this exceptional event, confirmed here to rank among the 10 largest moments ever published. Within the extremely complex regional plate tectonics pattern, the 1938 event took place in a region of sparse seismicity, and away from the presumed locations of block boundaries. The deeper than normal focus of the event agrees well with the generally minor level of reported damage, and with the generation of a relatively benign tsunami. Available modern focal mechanisms in its vicinity are too few and too scattered to allow any meaningful comparison, but the 1938 event shares its compressional axis with that of the smaller and deeper 1963 shock to the southwest, which probably expresses coherence in the regional contortion of the subducting Australian plate lithosphere.

European seismology has a great and ancient tradition. Its material traces — instruments, seismic recordings, letters between scientists — are a fundamental heritage from a scientific and historical point of view; often they are abandoned, scattered or even destroyed. It is necessary to start concrete, scientifically developed initiatives to stop such a heavy, progressive loss. Instruments, seismic recordings and scientific letters must be recovered and brought out on behalf of seismologists, using the tools of science history. Important results have already been yielded by two initiatives: the former has been carried out in Italy; the latter on an European scale. In Italy, the census of the historical potential of meteorological and seismic observatories, of seismic instruments and recordings has been taken, besides providing information about the availability of scientific correspondence archives. In Europe, the census taken by the Working Group of History of Seismometry allowed to be discovered information regarding the operative condition and the data availability of over 400 instruments since 1892.

Experiences made up to now have established clear goals, users, procedures and protagonists of the recovery. These initiatives must be taken in a co-ordinate and multidisciplinary reference framework, where each experience can be spread and shared by scholars and institutions.