24 channels seismograph, 24 bit real resolution Channels from 12 to 72 Embedded Pc - color touch screen monitor and rechargeable battery.

Transcription

1 24 channels seismograph, 24 bit real resolution Channels from 12 to 72 Embedded Pc - color touch screen monitor and rechargeable battery.

2 - PRESENTATION X610S seismograph is a compact and versatile instrument designed to perform all seismic prospections. High quality of measurements is ensured by hardware innovative architecture based on A/D converters with 24 bit resolution (SST technology), the highest among its category. That result can be achieved due to great investment to manufacture an innovative instrument worthy of M.A.E. long-term experience in seismology. Electric, electronic and software design is followed by many tests on field performed by very skilled customers who have achieved brilliant results in extreme environmental and climatic conditions. Possibility to add expansion boxes allows to get an high expandability through modules of 24, 48 and 72 channels, with consequent increasing of available measurement channels, in order to perform long arrays and increase depth of investigation. Managing software platform, already well-tested, can be managed by touch screen 12 monitor with transflective treatment, properly realized to manage all steps of configuration, recording, saving and visualization of data recorded on field. Accessories are realized to enhance positioning speed on site and at the same time to ensure performance and long resistance through years. 2

3 - SEISMOGRAPH : INSTRUMENT APPLICATIONS AND FEATURES Instrument frontal panel, made entirely of aluminum, has yellow engraved indications, visible in all environmental conditions and able to be preserved from usury which will inevitably arise with other kind of markings. Connections are all present on panel in order to comply to IP67 standard during transport phase with closed case. If monitor is damaged, it is possible to continue using instrument connecting an external monitor to VGA takeout present on panel through USB takeouts. To have remote control or for tele-service in case of problems, there is LAN port (Wi-Fi optional). Embedded GPS module allows to compute geographic coordinates of measurement and to automatically fill reference and quote fields of information window during measurements saving. Instrument management is simplified by graphic interface and by iterations through touch-screen system, which allows to perform all operations by touching icons directly on the screen. Mechanical design, both of panel and case, is a great compromise between rigidity and flexibility, ensuring maximum reliability in time and a correct absorption and reduction of transport solicitations so that to preserve inner components from possible damages. On lateral panels there are air nozzles necessary to cool inner circuits in order to avoid overheating with eventual damages. During use, correct cooling of inner components is managed by actioning of fans with filters against thin agents replaceable from outside. Accessories can be customized according to end-user requirements and to seismic prospections to perform; they complete equipment making it performing and logistically practice so that it is possible to use it in extreme environments. Care in projecting, realizing and calibrating each component ensures simple and fast on-site job. 3

4 Supplied cables are characterized by high resistance against dragging and usury in general. They are made of 12 takeouts with customized spacing (usually between 3 and 5 mt) to which geophones are connected. Cables conductors are flexible and present TPE insulator and yellow polish PUR sheath. Care in design, realization and test of each takeout ensures reliability and perfect working of each single measurement channel. Stainless steel connectors are housed in cases made of a special plastic material in order to ensure resistance in time and high flexibility. Single cable connections, as those of trigger system and power supply through external charge, are all present on frontal panel and are made of military connectors with bayonet coupling to speed up and ensure field operations. Starter or trigger system which detects energizing starting instant and starts signals recording can be provided in various typologies; sensitivity is managed through configurations parameters that can be selected during measurement. Due to great versatility and many automatic procedures of pre-recording test, from geophones connection to background noise of investigated site, seismic signals recording is performing and manageable. Acquisition software allows a first analysis of recorded data directly on site, also for each single wave, by visualization of seismographs with few and simple operations. Data saving is done on a solid-state internal hard disk for a better protection in case of impacts, or on USB external memory. Touch-screen system allows to perform all operations by touching objects directly on high visibility display, which is properly designed to be used in all environmental conditions. In case of monitor damages, it will be possible to use seismograph connecting an external monitor to VGA takeout present on panel together with keyboard and mouse. User is guided in selecting options from a starting shell where it is possible to: - check technical documentation; - start recording and configuration apps; - start utilities of data saving, remote assistance; - start instrument automatic turning off. To check instrument functioning status, on applications bar of the display there are all information related to battery voltage, working temperature, available space and time. All operations can be managed in an intuitive way by touching display with proper pen; after a short use of interface for a first practical exercising, operator can observe how easy-to-use it is. A good knowledge of Microsoft Windows XP operating system and management of files and peripherals of a modern personal computer is required. Recording and data saving can be done on SSD internal memory and on USB disk on key. Checking during recording is possible through many tools present on software main screen. Recording parameters setting such as sampling frequency and recording duration are strictly related to the kind of survey to perform therefore it is a fundamental step for a correct execution of investigation. 4

5 High number of channels available is managed through commands which allow to specify gain for each channel and allocate belonging groups in order to change amplification simultaneously for all geophones belonging to the same group or for a single receiver; in this way the array is modular and can be configured according to customer needs. To increase signal/noise ratio, it is possible to perform iterations procedures on single channels which allow to perform sum, difference and replacement of recorded seismic traces; these operations are important for some kind of prospections as bore-hole investigations. X610S technical specifications Configuration 24/48/72 differential channels for a greater immunity to the electric noise, to be connected using from 1 to 6 arrays. Converters: 24 bit resolution, sigma-delta technology A/D Conversion: 24 bit with a sigma-delta technology dedicated to the single channel Dynamic range 144dB of system, 134dB instantaneous at 2mS Distorsion 2 ms Maximum distorsion +/ % Band width 2Hz-30KHz Common mode rejection 110 db a 60 Hz (DC to 8kHz) Diaphony -120dB at 20 Hz 5

6 Influence among the channels (CROSSTALK) Inexistent thanks to the presence of the converter for every single channel Noise threshold of the programmable amplifier 27nV Trigger precision 1/30 of the sampling time Maximum amplitute of the input signal 10Vpp, 0dB Maximum range of the input signal +/-5V Input impedance 0dB Input impedance at 1000 samples/second 20Mohm Amplitude levels 0 db, 6 db, 12 db, 18 db, 24 db, 30 db, 36 db settable singularly for every channel or for groups of channels which can be freely organized Noise 2 ms, 36dB Anti-alias filter -3dB,80% of the Nyquist frequency,-80db Pre-trigger time 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 50, 100, 200, 300, 400, 500ms Sampling interval 1/30, 1/15, 1/7.5, 1/3.75, 0.5, 1.0, 2.0, 10.0, 20.0 ms Number of samples per event Settable from 1024 to with increases of 512 Recording memory samples Interfaces available LAN, USB, VGA Channels Setting from 24, 48 r 72. Possibility to use from 1 to the maximum number of channels installed for every acquisition Internal auto-calibration of the converters before every acquisition Digital filters Geophones test Visualization in real time of the signals coming from the geophones Data archive Trigger Data format Operating system Power Supply Display Weight Dimensions Environmental conditions Configuration Automatic test for detecting any cable interruption or broken geophones positive, negative with threshold settable from software SEG-2 standard (32-bit long integer) or ASCII WINDOWS EMBEDDED It requires 12V 2,5A from external battery in the 72 ch. configuration LCD 12.2" with optical bonding touch screen integrated 10Kg 48.5 x 39.2 x 19.2 cm anti-crushing copolymer case -20/80 C 24/48/72 differential channels for a greater immunity to the electric noise, to be connected using from 1 to 6 arrays. 6

7 - POSSIBLE APPLICATIONS Due to new MAE 24 bit acquisition board, which adopts a digital A/D converter for each inlet channel (SST technology) X610S seismograph is ideal for all kind of active and passive seismic prospections and also for structural surveys on buildings ( acquisitions of vibrations through accelerometers or low frequency seismic sensors, topographical investigations etc ). It is designed to record subsurface seismic prospections in an easy and reliable manner from subsurface seismic to bore-hole seismic and, through particular optional units, it can be used also to investigate most common structural elements. It is ideal also for seismic monitoring and for dynamic analysis on building due to great recording memory which can record up to samples, allowing to get great data quality (signals) with high sample frequencies and / or recording environmental vibrations for many hours. Some of the most common seismic prospections are listed below. REFRACTION SEISMIC Through refraction seismic it is possible to evaluate subsurface geometries and thickness, define velocity of the layers and obtain soil elastic-dynamic characterization through P and SH waves recording on surface with proper geophones (vertical and horizontal). Performing different shot points along the line it is possible to increase seismic section details in order to better evaluate single refractors trend which can be identified through dromocrones analysis (timespace lines). SEISMIC TOMOGRAPHY Recorded seismic signals can be interpreted through specific softwares in tomographic technique, so as to limit problems caused by speed inversion layers (ghost horizon) or reduced thicknesses that are 7

8 limits of traditional methods (Generalized Reciprocal Method). That kind of restitution is extremely precise and excellent for detection of buried structures, cavities, reconstruct and border landslide volumes. Inversion process models signal propagation multiple paths which concur to a first arrival and also models diffraction, refraction and seismic waves transmission. X610S seismograph is designed for reflection seismic prospections with high and low resolution; method is most used by operators particularly skilled in data processing and is dedicated both for civil engineer, where it is required a detailed section of subsurface, both for research purpose of reconstructing structural and stratigraphical disposition of geological corps located in depth. Unlike refraction seismic, not only elastic wave first arrival to single geophone is measured, but it is performed an accurate analysis of wave trains received through which it is possible to recognize signals coming from soil separation surfaces characterized by different seismic velocities. Final result will be a graphic script where trend of reflection surfaces from subsurface is underlined (seismic reflectors) which will indicate presence of discontinuities, deposits geometry, stratification, discordance areas, faults, overcrowdings etc Arrays can be moved translating or using roll along cables to be able to reach deepest layers and performing on different geophones seismic signal recording coming from the same reflector, getting an amplification of signal / noise ratio. Final result is a representation, in time units, of a subsurface vertical section along profile line. Each seismic reflector reveals presence of a discontinuity (layer, discordance, tectonic contact. BORE-HOLE SEISMIC Bore-hole seismic tests want to determine propagation speed of compression P waves and shear S waves; they are particularly useful to determine Vs30 parameter for structural projecting. Down-hole method requires power source on surface and sensors inside hole. 5 components particularly assembled geophones are used inside the hole and fixed at increasing depth on hole walls properly conditioned; through surface energization of the soil and measuring arrival times of first pulse to geophone, it is possible to determine speed and elastic-dynamic modules. 8

9 Cross-hole test is performed with at least 2 survey holes; in one of them triaxial geophone is placed, while in the other energization takes place. Power source must be able to generate elastic waves with high frequency and full of energy, with directional wave shake which means that it is possible to get mainly compression and/or polarized shear waves on vertical planes. It is also possible to perform seismic tomographies between investigation holes which are useful to locate fractured areas (mechanically deteriorated) and more in general to detect speed anomaly areas into investigated soil. For the above mentioned surveys it is necessary to arrange properly equipped holes. SURFACE SEISMIC: MASW and Re.Mi Geophysic exploration through surface waves allows to obtain in simple and economic way speed propagation of S waves into subsoil. MASW method (Multichannel Analysis of Surface Waves) allows to determine Vs30 speed profile. It goes behind some limitations of refraction method such as speed inversion. It does not require long recording time and gives good results also if environmental noise is present. 9

10 Rayleigh waves, in a layered means, are dispersive because they propagate with different phase and group speeds. They are registered along geophones array energizing artificially and then they are analyzed through complex computing techniques based on a recognition of multilayer soil patterns. Observing frequency spectrum it is possible to underline that S wave propagates at variable speed according to its frequency as result of dispersion phenomena. Once performed picking on f-k spectrum or on dispersion curve given by field data, through inversion process it is possible to get speed velocity with depth which allows to define Vs30 parameter. Re.Mi. analysis (Refraction Microtremor) is a passive seismic technique to record microtremors coming from natural sources (wind, sea, human activities), through multi-geophone dispositions. With this methodology it is possible to study dispersion properties of Rayleigh waves. During analysis, speed spectrum of different temporal windows are determined and between them it is chosen the most clear in order to detect which wave to invert, such as MASW analysis; however, contrary to MASW, this is a method used to investigate particularly noisy areas and has better resolution in determining deeper layers. PASSIVE SEISMIC:Horizontal to Vertical Spectral Ratio (HVSR) Sensors are usually tri-axial with low frequency (1, 2 Hz). This methodology can detect resonance frequency of soil and is based on background noise recording in time domain and later processing in signal frequency domain. It is performed placing a tridimensional geophone on the ground and recording seismic noise in different temporal windows. Subsequently, study of spectra obtained from deconvolution in signal frequency domain recorded for three components of soil motion and techniques application on spectra ratio, allows to define and dimension eventual local seismic amplifications and site frequency. Useful in presence of great impedance contrasts to estimate seismic bedrock depth, it is particularly used in microzonation seismic studies. 10

11 This kind of survey versatility allows also to get building resonance frequency to compare it with soil frequencies. This technique is used to get information about eventual effects of seismic waves dynamic amplification in emersion. Microtremor measurements can be also performed in linear arrays to define tectonic structures and fault lines. SEISMIC MONITORING Instrument efficiency allows also to perform so-called trigger (or threshold) seismic vibrations monitoring, so it can be included in Non destructive Tests range of equipments mainly used in structural monitoring and dynamic surveys on buildings. In stand alone seismic recordings, instrument can start recording as soon as an event which overcomes trigger threshold selected during configuration occurs. It allows to evaluate seismic vibration consequences generated by city traffic or temporary construction site on buildings, infrastructures and house in general. Through this methodology it is possible to monitor in continuous preservation status of monuments or buildings of great artistic value. 11

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