ISSN 07479239, Seismic Instruments, 2014, Vol. 50, No. 1, pp. 67–74. © Allerton Press, Inc., 2014. Original Russian Text © A.A. Stepnov, A.V. Gavrilov, A.V. Konovalov, L. Ottemöller, 2013, published in Seismicheskie Pribory, 2013, Vol. 49, No. 2, pp. 27–38.
New Architecture of an Automated System for Acquisition, Storage, and Processing of Seismic Data A. A. Stepnova, A. V. Gavrilova, A. V. Konovalova, and L. Ottemöller b a
Institute of Marine Geology and Geophysics, Far Eastern Branch, Russian Academy of Sciences, ul. Nauki 1b, YuzhnoSakhalinsk, 693022 Russia b Department of Earth Sciences, University of Bergen, Postboks 7803, Bergen, NO5020 Norway email:
[email protected],
[email protected],
[email protected],
[email protected]
Abstract—Features of the new architecture of an automated system for acquisition, storage, and processing of seismic data are considered in detail. The system is based on SEISNET and SEISAN software. Specific technologies, software, and examples of the interconnection of system components are presented. The func tionality of the system and the data life cycle are shown. An example of the implementation of the new archi tecture in the existing seismic monitoring network in the northern part of Sakhalin Island is examined. Keywords: automated system, data acquisition, network of seismic stations, earthquake, SEISAN, SEISNET, Linux, database, data life cycle, telemetry DOI: 10.3103/S0747923914010083
it is necessary to solve the problem of the automation of processes such as the transmission of data from remote stations, automatic detection of seismic events in the stream of digital data, and rapid determination of source parameters of earthquakes under conditions of the unstable communication with remote seismic stations. This problem can be solved by an automated sys tem for the acquisition, storage, and processing of seismic data based on advanced technologies and soft ware. The review of existing software makes it possible to select a number of systems for the seismic data acqui sition automation. The EARTHWORM system (Johnson et al., 1995) has been in the process of development since 1993. It was originally created by the United States Geological Survey (Reston, Va.). It is currently being developed as a separate project (Earthworm Documentation V7.5. http://folkworm.ceri.memphis.edu/ewdoc/). The EARTHWORM software concept requires the central nervous system, which continuously receives data from a plurality of sensors in real time. The EARTH WORM central system reads and processes data received from memory using software modules. As a result, the software automatically picks arrival phases, informs about detected events, and saves data to a disk. Since the EARTHWORM system has a modular structure, its functionality depends on the specific configuration. The data storage structure is not regu lated. The SEISNET system (Ottemöller and Havskov, 2004) was developed at the Department of Earth Sci
INTRODUCTION Sakhalin Island is a region of Russia with a high rate of tectonic activity. However, there are oil and gas production facilities and facilities for the transporta tion of minerals on the island and its coastal offshore. Sakhalin1 and Sakhalin2 are the most wellknown projects implemented there. The main oil and gas facilities in the north of the island are located in the zone of active tectonic faults of different rank and age. These faults were revealed as a result of numerous geological and geophysical, seis mological, and paleoseismic studies (Bulgakov et al., 2002; Katsumata et al., 2004; Kharakhinov, 2010; Konovalov et al., 2012). These zones are characterized by high seismic potential. All these factors formed the basis for the develop ment of the seismic monitoring system (Konovalov et al., 2010) including the monitoring of induced seis micity. To date, the seismic monitoring system involves an automated workstation of a seismologist based on SEISAN software (Ottemöller et al., 2011; Konovalov et al., 2011). A key drawback of the system is the lack of functional capabilities for rapid data processing, since seismic stations are maintained in the postpro cessing mode, and data acquisition is carried out every 2 to 3 months. However, recently, telecommunica tions infrastructure has been rapidly developing in the region making it possible to create a network of telem etry stations. Thus, because of the high frequency of seismic events in the north of Sakhalin Island in the first place 67
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ences , University of Bergen (Norway). It is capable of data acquisition from remote stations in the postpro cessing mode. The SEISNET system supports proto cols such as AutoDRM (Kradolfer, 1996), SEISLOG (Utheim and Havskov, 1999), etc. In addition, it makes it possible to acquire data stored on a remote file server via FTP (Postel and Reynolds, 1985). The applicability of the SEISNET system is not limited to data acquisition. It makes it possible not only to arrange the received data streams in the SEISAN data base but also to use the functionality of the system for the automated data processing. The project SEISCOMP (Weber et al., 2007) was developed at the GFZ German Research Centre for Geosciences (Potsdam, Germany) and gempa GmbH (Potsdam, Germany) within the program GEOFON (Geofon Program. http://geofon.gfzpotsdam.de/). The current version of the system uses the SEIS COMP SEEDLink protocol (Hanka et al., 2000) to acquire data in real time and the ArchLink protocol (Documentation of the Archlink. http://www. seiscomp3.org/wiki/doc/applications/arclink) to acquire data in the postprocessing mode. It supports the storage of data in popular database management systems (DBMSs) such as MySQL and PostgreSQL. It also has a set of applications for automated data pro cessing. The use of SEISCOMP implies its own struc ture of data organization, which makes the product incompatible with the SEISAN database. We would like to mention the system of seismic observations in Kamchatka (Gordeev et al., 2006) for which the software for instrumental data acquisition and analysis is developed (Drosnin and Drosnina, 2010). Currently, the license for this software is not published, and source and binary files are not in the public domain. In the considered system attention should be paid to the functionality of the SEISNET software, which determined the choice of this program, i.e., a deep integration with the seismic software package SEISAN, support of the operating system Linux, a free software license, and data acquisition in the post processing mode using the protocol FTP. Furthermore, in this paper the data life cycle in the system from the seismic receiver to the results of instrumental data processing is analyzed. HARDWARE AND SOFTWARE SYSTEM IMPLEMENTATION The developed system is based on the concept of the virtual seismic network (VSN) (Ottemöller and Havskov, 1999) in which the terms seismic node and data processing center (DPC) can be singled out. The VSN is a centralized network where digital data acquired from remote nodes enter the DPC, where data is subsequently processed, analyzed, and stored. Data enter the system in nearreal time, i.e., data is
acquired from all the nodes in the continuous mode, the delay for individual stations is less than 60 minutes. The software, which is part of the implemented sys tem, deserves special attention. 1. GNU/Linux is the operating system (Stallman, 2012). 2. SEISAN is the software for processing and anal ysis of seismic data (Ottemöller et al., 2011). 3. SEISNET is the automated software for seismo logical observations (Ottemöller and Havskov, 2004). 4. XEN is the hypervisor for platforms IA32, x86, x86–64, Itanium, and ARM (Barham et al., 2003; Colp et al., 2011). It should be noted that systems SEISNET and SEISAN are deeply integrated with each other. They both use a single database SEISAN and some single set of binary and configuration files. A free operating sys tem, Linux, and XEN virtualization software provide unlimited opportunities for the system (Fig. 1). The store has a separate hardware platform and is based on the concept of a Storage Area Network (SAN) (Padovano, 2003). Access to the data is carried out by protocols ISCSI (Satran et al., 2004), which is more efficient compared to Fibre Channel technolo gies traditional for SAN. Since the system has been designed to be fault tolerant with shared access to data, OCFS2 is used as the file system (Mushran, 2008). For storage of continuous digital data and their pro cessing results the database SEISAN is used. A set of configuration files (for example, STATION0.HYP, SEISAN.DEF, MULPLT.DEF), calibration files of seis mic stations, and binary files of the software SEISAN are located in corresponding directories of the repository along with the database. A special set of rules regulating the collective work on a single set of data and configuration files has been developed. Global configuration files that determine the velocity model, calibration parameters of stations, and settings of the visualization software can be changed only by the administrator of the system. Cal ibration files of stations also have the status of global parameters and are available in the CAL directory of the SEISAN installation package. After making changes to the global parameters of the system all the events in the database are updated with the command “update.” On the other hand, each user can create their own system files in the home directory. If such configuration files are found in the user’s directory, the system will use the user parameters instead of global ones. These changes will not affect other system users. This approach allows us to provide each user the opportunity to change the global parameters only within their own session. Incoming digital data are divided into two arrays. The first one contains continuous waveforms that are used for searching and detecting seismic events. The second array is used to store the selected events associ ated with a particular event in the database REA of the SEISMIC INSTRUMENTS
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Storage DB SEISAN:
Programs SEISAN/SEISNET:
– waveform data
– stations calibration files (CAL) – global configuration files
– routine data processing
results
DOM 0
DOM 1
DOM 2
DOM 3
Management Service
Data Exchange Service
Service of applications and terminal access
Monitoring Service
XEN
Fig. 1. The general model of the system located in a data processing center (DPC).waveform data
SEISAN installation package. Selected waveforms are formed during data processing. They are represented in the SEISAN format. Each data set consists of threelevel hierarchically nested folders. 1. NNNNN is the short symbolic name of the sta tion (no more than five English characters). 2. YYYY is the year. 3. MM is the month. Here is an example of such an archive: /WAV/ARGI_/2011/01/, where WAV is the root directory, where are all the waveforms are stored, ARGI_ is the directory for waveforms of a particular station, 2011 is the year, and 01 is the month. Selected events are placed in the directory IMGG in the catalog WAV. The system architecture can be logically divided into the following subsystems ⎯Acquisition and transmission of data. ⎯Storage of data and their processing results. ⎯Processing of seismic data. ⎯Graphical representation of data and results of their processing. ⎯Automatic control of the monitoring network state. However, in practice, specific programs and system modules include the functional, which overlaps the scope of application of the abovementioned sub systems. In terms of implementation, maintenance, and support the concept of a service, which is imple mented in a virtual environment and operates in its own environment of the operating system Linux, is more convenient. Four basic system services implementing the func tional of above mentioned subsystems have a concur rent access to stored data. These services are running in separate virtual containers with complete redun SEISMIC INSTRUMENTS
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dancy. System services are connected by a protocol stack TCP/IP (Socolofsky and Kale, 1991). 1. Management service is a service designed to manage the system. At this node a large range of aux iliary software is deployed designed exclusively for debugging the system as a whole and its individual components. At this point the system administrator conducts routine, emergency, and commissioning. 2. Data exchange service is a service that acts as the collector of data from seismic nodes within the VSN concept and data received from the AutoDRM service and databases of other seismological centers. This is where the system SEISNET operates, and the rules for data acquisition are set. The area of responsibility of this node includes recording of digital data in the data base SEISAN, implementation of custom program scripts that use the software for the automatic detec tion of seismic events (CONDET), and autodetection of arrival times and amplitudes of seismic phases (AUTOSIG and AUTOPIC). (CONDET, AUTOPIC, AUTOSIG are all part of the software SEISAN). 3. Service of applications and terminal access is the main service that provides interaction of operators and analysts (users) with the system. Users connect to the host via the terminal using the SSH2 protocol (Ylonen and Lonvick, 2006) and X Window System software (Scheifler, 2012). Remote users running MS Windows use PUTTY (Tatham, 2011) and Hming (Xming X Server for Windows. http://www.straight running.com/XmingNotes/) for connections. In this case, all the features of the software SEISAN, data storages, and a set of additional software, which is located in user’s personal directories, are available to the users. 4. Monitoring service is the service for the moni toring of the system. The monitored elements include
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Acquisition and allocation of data in the database SEISAN
AutoDRM Service
Visualization Seismic bulletins, waveform data Data from other networks Virtual private network
Data Exchange Service
Other programs
Routine data processing (SEISAN)
Statistics
Remote seismic node
Reading Data stream
Service of applications and terminal access
GPRS module Analysts, operators
Update/Write
Digitizer
Service PC Seismometer
Preparing data to be transmitted to the data center, conversion into MiniSEED, etc.
Shared storage
DPC
Fig. 2. The data life cycle in the automated system.
communication channels, amount of incoming data, results of script execution, number of terminal users, etc. This service is implemented using Web technolo gies. Such an approach in the implementation, where each service with its range of tasks is localized in a vir tual environment, makes it possible to create a modu lar system, which significantly facilitates its mainte nance and scaling. The data life cycle in the system is shown in Fig. 2. An example of the system dialog box is shown in Fig. 3. In this example an open terminal session of the operator is shown, where the operator commands are executed remotely using the console connected via SSH2, and graphics applications are displayed on the local system. They obtain information over an estab lished connection. TECHNICAL SYSTEM COMPONENTS Currently, in the north of Sakhalin Island a local network of eight seismic stations is functioning (Fig. 4). Stations SABO, CHIVO, NGLK, ARGI, and LNSK are connected into the VPN network built on the basis of GPRS, XDSL, and IPSEC technologies. Each station is a remote seismic unit within the con cept of VSN and is a part of a unified system of seismic monitoring. The node has a typical organization and consists of the recorder and industrial service com puter (PC), which interact with each other locally using Ethernet.
Such an organizational model with a service PC was chosen for the implementation for several reasons. First, there was a need to create the encrypted data channel. Second, it was necessary to provide prepro cessing of recorded data for the transfer via communi cation channels and import to the central database. Third, there was a need in the extended data manage ment interface and guaranteed data acquisition in the event of emergency situations (e.g., communication problems). Thus, the service PC significantly expands the functionality of the recorder and provides reliable data transfer. When designing the system special emphasis was laid on technical and operational conditions of the equipment installation location where the tempera ture in the winter falls to –40°C. Therefore, the equip ment with the industrial design was selected (Fig. 5). Timetested and used in different operating condi tions shortperiod seismic sensors LE3Dlite (Lennartz Electronic, Germany) (Technical Specifications of a LE_3DLite MKII Seismometer, Lennartz_Electronic. http://www.lennartz_electronic.de) are used as seismic sensors. The seismic sensor has an eigen frequency of 1 Hz and its amplitude–frequency characteristic (AFC) at frequencies above its natural one is set by a constant factor, i.e., the sensor sensitivity. Domestic digitizers Delta03 (OOO Logis, Russia) (Product catalog of Logicheskie sistemy LLC. http://www.logsys.ru), which proved to be reliable and relatively inexpensive devices (Gavrilov et al., 2010), SEISMIC INSTRUMENTS
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Xming X 2011 – 01 – 21 – 2136 – 00S. IMGG__021 2011 124 2139 22.7 L Plot start time: 2011
50.707 143.658 24.1 SAK 1 24 0.006 21:26
(a)
5 0.4 4.7 LSAK
ARGI SHZ 00 IM ARGI SHN 00 IM ARGI SHE 00 IM CHIVO SHZ 00 IM CHIVO SHN 00 IM CHIVO SHE 00 IM OKHA SHZ 00 IM OKHA SHN 00 IM OKHA SHE 00 IM SABO SHZ 00 IM SABO SHN 00 IM SABO SHE 00 IM TYV SHZ 00 IM TYV SHN 00 IM TYV SHE 00 IM Event #
43 Wadati diagram:
jamm@seisan – term:~ [ jamm@seisan – term:~ ] S Is 2011 – 01 – 01 – 0603 – 425. IMGG__021 HYTEMP. XXX SoftUpdateLog. txt a. out epimap. are epimap. cor epimap. eps epimap. inp epimap. num epimap. out filenr. lis focmec. dat focmec. inp focmec. lst [jamm@seisan – tern: ~] $ eev 20110124
# 1 # 4 # 1 # 5
focmec. out gmap. cur. kml hyp. out hypinst hypinv. mod hypinv. sta hypsum. out index. codaq index. out mulplt. out norhin. out out print. out pspolar. inp
S – P t i m e
scratch1. out scratch2. out scratch3. out select. inp select. out signal. out testdir testfile ttlayer. out ttplot. eps ttplot. out wad_plot. eps waveform_names. out
2011 1 Reading events from base IMGG_ 72 40 24 Jan 2011 13:18 0 L ? 41 24 Jan 2011 15:04 1 L 52.227 142.928 9.4 ? 42 24 Jan 2011 15:37 0 L ? 43 24 Jan 2011 21:39 22 L 50.707 143.658 24.1 ?
s e c o n d s
T0 2139
23. 0 VP/VS
1. 81 STAT CO IPHASW HRMM SEC OKHA SZ IP 2140 y. 83 OKHA SE ES 4 2140 43. 88
35 30 25
(c)
20 1. 1LSAK
15
0.5 1.9LSAK 0.2LSAK
10
0.4 4.7LSAK
(b)
0
35 40 45 50 55 60 65
STAT PS S – P STAT PS S – P 9. 87 ARGI 13. 85 TYV NGLK 15. 93 OKHA 36. 05
Ptime, s
Fig. 3. An example of the terminal access to an automated system from a workstation running the Windows operating system. The window of visualization and waveform processing program (a), SSH session (b), a window representing the Wadati diagram given in the figure (a) for a local earthquake (c).
GNU/Linux was chosen for the additional PC. The basic configuration of the seismic unit includes a FTP server to transfer data. The authors developed an application that runs under the Linux operating sys tem and implements the communication protocol with the software part of the recorder Delta03, which runs on schedule and downloads the data on the PC hard disk. The application keeps a log file that stores data on downloaded files and emerging crashes. The data download speed from the logger is about 200 KB/s in the case of the direct connection to the PC station. At that downloading speed, a continuous file with an hour long recording in six channels and the SEISMIC INSTRUMENTS
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142°
144° N
1 W
2
E S
54°
Sakhalin Island
54°
OKHA NKL
53°
SABO
CHIVO 52° NGLK
Okho tsk
53°
The S e a of
The industrial computer ECW281BWD/N270/1Gb (http://www.ieiworld.com/product_groups/industrial/ content.aspx?gid=09049552811981014603&id=&cid =0833062854398209600908141362043512651539#. UMZd7Mf9t8) is used for the PC. This model has an extended source voltage range (from 9 to 36 V) and passive cooling. The use of the solidstate hard drive as a data storage made it possible to get rid of moving parts in the design and make it insensitive to shocks and surges. The operating temperature range of the equipment is from –10 to +50°C, which makes it possible to operate under more severe con ditions than office PCs.
140°
52°
ARGI LNSK 51°
Tatar Strait
were used as digital recorders. The sample rate at all stations is 125 samples per second. The time synchro nization is carried out using the builtin GPS receiver, and the formation of the reference realtime clock fre quency is conducted using a highprecision, highly stable, and temperaturecontrolled oscillator.
141°
51° TYV
143°
50° 145°
Fig. 4. The local network of seismic stations in the north of Sakhalin Island. Seismic monitoring stations (1) and regional stations (2).
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Fig. 5. Equipment in the seismic pavilion.
data acquisition frequency of 125 Hz loads for 1 min. For a threechannel recording the time corresponds to 30 s. In order to unify the format of the recorded data in the SEISNET the developed application converts files recorded by Delta03 in native formats ADB and DDB to a universal format MiniSEEDSteim1. An hour long file in the MiniSEEDSteim1 format is formed as follows: YYYYMMDDHHMM SSI.NNNNN_CCC where YYYY is the year, MM is the month, DD is the day, HH is the hour, MM are minutes, SS are seconds, I is the identifier of the file format (in this case, I = M, which corresponds to the MiniSEED format), NNNNN is the short symbolic name of the station (no more than five characters in English), and CCC is the number of channels. The listed timing indicators correspond to the beginning of the recording of the next file fragment (for example, 20110101000000M.ARGI__003). Data from the seismic station are recorded to the PC directory specified in the configuration file con fig.cfg. The directory with the archive of digital recordings in the MiniSEED format can be accessed via the FTP protocol for the further data transfer. Files are organized in the “flat” structure. All the files are located in the same directory. By default, the path /var/archive is specified in the configuration file. Log files of the application are stored in a separate folder. OnCell5104 (Moxa Cellular Router. http://www. moxa.com/product/oncell_5004_5104.htm) is used as a 3G router. The device combines a 3Gmodem with two SIM card slots, switch, and VPNrouter. The router automatically connects to GSM, allocates addresses to devices on the local monitoring network,
forwards data packets from the LAN to the Internet, and creates a VPN channel with the DPC. It simplifies the set of software on the computer station and reduces the load on it. The router operates in temper atures ranging from –30 to +70°C. In order to provide power to the equipment a secondary power supply is used, i.e., redundant SKATV.12DC18 (Manual SKATV.12DC18 App. 5000. http://www.bast. ru/bastion/ product/pasport/skat_v12dc18_5000.pdf). The unit is designed for equipment with the operating voltage of 12 V. The devices are supplied by the net work if there is power. If the mains voltage is turned off the unit automatically switches to battery power. It makes it possible to operate under conditions of unsta ble power supply and save battery life. High load capacity of this battery model makes it possible to con nect the whole set of equipment leaving large reserve power and to quickly recharge a high capacity battery when the power is restored. Information from the regional station NKL in the form of the station bulletin enters the system by editing files of the SEISAN database. In 2009, within the tar geted comprehensive program of basic research of the Far Eastern Branch, Russian Academy of Sciences “Recent Geodynamics, Active Geostructures, and Natural Hazards of the Far East of Russia,” a broad band seismic station was established (Khanchuk et al., 2011). In 2012, the data communications system of this station was significantly upgraded, which provided researchers with continuous streams of instrumental data in the near realtime mode. Digital data received from the station enter the Computing Center, Far Eastern Branch, Russian Academy of Sciences. Information from regional stations and TYV and OKHA arrives in real time in the Sakhalin Branch, SEISMIC INSTRUMENTS
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Geophysical Service, Russian Academy of Sciences (SB GS RAS). In the system database these data are acquired in the postprocessing mode by manual add ing to the archive after the conversion of data into the MiniSEED format. In the future, a better integration of regional and global seismological networks is planned in order to organize a unified system of seismic monitoring in the north of Sakhalin Island. It is possible to estimate the amount of data that will be fed to the system from the local monitoring net work over 1 year up to 100 MB based on the specifica tions of the recording equipment and on experience with digital data formats. A station which has three recording channels gen erates approximately 1500 B/s of raw data. Conse quently, eight stations will generate approximately 12000 B/s of raw data. Based on the above, we obtain the following amount of data per day ( 1200 × 60 × 60 × 24) ∼ 0.97 GB/day. 3 1024 In the Institute of Marine Geology and Geophys ics, Far Eastern Branch, Russian Academy of Sciences the MiniSEED format is commonly used. In order to unify raw data all the waveforms are converted to this format. In practice, the conversion of raw data into the MiniSEED format makes it possible to compress it by a factor of 0.67. Consequently, for a year from eight stations we obtain about 237.25 GB of data in the MiniSEED format. CONCLUSIONS A new architecture of the processing system of seis mic data is developed, which makes it possible to acquire data from remote seismic stations, organize continuous streams of data in a database, and carry out routine processing of instrumental data in the auto matic mode. Seismologists are provided with the func tional interface to work with data and results of their processing. Thanks to the package of seismic programs SEISAN/ SEISNET, Linux operating system, and virtualization based on XEN, the system implemented in the data center of the Institute of Marine Geology and Geo physics, Far Eastern Branch, Russian Academy of Sci ences has a highly scalable, highly reliable, and modu lar architecture. In the future individual modules (ser vices) can be transferred to another more powerful hardware without stopping the whole system. How ever, such an element of the system as a remote node ensures data transfer even under an unstable channel of communication, which is important for the current operating conditions of a local network of seismic sta tions. Thus, on the basis of components of domestic seis mological equipment and specially designed programs a flexible architecture has been created that can adapt SEISMIC INSTRUMENTS
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to a wide range of problems of modern seismology. At the moment, this architecture is implemented in the Institute of Marine Geology and Geophysics, Far East ern Branch, Russian Academy of Sciences in the seis mic monitoring system in the north of Sakhalin Island. The further development of the implemented system will create a stable foundation for the integration of the local network of stations of Sakhalin Island with global and regional seismological networks. ACKNOWLEDGMENTS We are grateful to the team of seismologists of the Department of Earth Sciences, University of Bergen (Norway) who developed a package of seismic pro grams SEISAN/SEISNET, placed it in the public domain, and provided its source code. REFERENCES Barham, P., Dragovic, B., Fraser, K., Hand, S., Harris, T., Ho, A., Neugebauer, R., Pratt, I., and Warfield, A., Xen and the art of virtualization, Proc. 19th ACM Symposium on Operating Systems Principles, New York, 2003. http://www.cl.cam.ac.uk/research/srg/netos/papers/2003 xensosp.pdf Bulgakov, R.F., Ivashchenko, A.I., Kim, Ch.U., Sergeev, K.F., Strel’tsov, M.I., Kozhurin, A.I., Besstrash nov, V.M., Strom, A.L., Suzuki, Y., Tsutsumi, H., Watanabe, M., Ueki, T., Shimamoto, T., Okumura, K., Goto, H., and Kariya, Y., Active faults in northeastern Sakhalin, Geotectonics, 2002, vol. 36, no. 3, pp. 227–246. Colp, P., Nanavati, M., Zhu, J., Aiello, W., Coker, G., Dee gan, T., Loscocco, P., and Warfield, A., Breaking up is hard to do: security and functionality in a commodity hypervisor, 23rd ACM Symposium on Operating Systems Principles, Cascais, 2011, pp. 189–202. http://www.cs.ubc.ca/ ~andy/papers/xoarsospfinal.pdf Droznin, D.V. and Droznina, S.Ya., Interactive DIMAS program for processing seismic signals, Seism. Instrum., 2011, vol. 47, no. 3, pp. 215–224. Gavrilov, A.V., Konovalov, A.V., and Nikiforov, S.P., Results from field and stationary tests of the seismic signal recorder Delta 03, Seism. Instrum., 2011, vol. 47, no. 3, pp. 271–277. Gordeev, E.I., Chebrov, V.N., Levina, V.I., Sinitsyn, V.I., Shevchenko, Yu.V., and Yashchuk, V.V., The system of seis mic observations in Kamchatka, Vulkanol. Seismol., 2006, no. 3, pp. 6–27. Hanka, W., Heinloo, A., and Jackel, K.H., Networked seismographs: GEOFON realtime data distribution, ORFEUS Electronic Newsletter, vol. 2/3, 2000. http:// www.orfeuseu.org/Organization/newsletter.html. Johnson, C.E., Bittenbinder, A., Bogaert, B., Dietz, L., and Kohler, W., Earthworm: a flexible approach to seismic net work processing, IRIS Newsletter, 1995, vol. 14(2), pp. 1–4. Katsumata, K., Kasahara, M., Ichiyanagi, M., Kikuchi, M., RakSe, Sen., ChunUn, Kim., Ivaschenko, A., and Tatevos sian, R., The 27 may 1995 MS 7.6 Northern Sakhalin earth quake: an earthquake on an uncertain plate boundary, Bull. Seismol. Soc. Am., 2004, vol. 94, no. 1, pp. 117–130.
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SEISMIC INSTRUMENTS
Vol. 50
No. 1
2014
