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Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes

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Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes Extended Summary 本文は pp.227-232 Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes Takashi Maeda Student Member (The University of Tokyo, [email protected]) Tadashi Takano Member (ISAS/JAXA, [email protected]) Kozaburo Inoue Non-member (ISAS/JAXA, [email protected]) Teruo Kato Non-member (ISAS/JAXA, [email protected]) Keywords: seismo-electromagnetic effect, microwave emission, earthquake, satellite, data analysis system, rock crash It is reported that various anomalies of the electro- magnetic field or the ionosphere have been observed before earthquakes. The frequency used to observe these phenom- ena ranges from ULF(～3Hz), ELF(3～3000Hz) or VLF(3～ 30kHz) to HF(300～3000kHz) or VHF(3～300MHz). How- ever, the microwave in GHz band has hardly been used. On the other hand, it was experimentally shown that rock crash by static pressure caused the radio wave emission at 300MHz, 2GHz and 22GHz. This result suggests the microwave is emitted on the occasion of earthquakes. The microwaves (S- band, 2GHz) are used for the communication between track- ing stations and earth-orbiting satellites launched by Insti- tute of Space and Astronautical Science (ISAS). The S-band microwave power level received by a satellite is measured and stored in the database of ISAS, which is called ‘SIRIUS’, all Fig. 1. System flowchartforextraction of the spe- thewhile orbiting. There are possibilities that the microwave cific satellite data emissions associated with earthquakes are detected in the database SIRIUS. Encouraged by the above circumstance, we have developed the computer system to extract the S-band microwave power level corresponding to major earthquakes which occurred all over the world from 1986 to 2004, and investigated the re- lation between the S-band microwave power level and earth- quakes. Figure 2 shows the epicenter of the earthquake which oc- curred on August 8, 1993 at 8:34:24 UT (geographic coordi- nates: 12.982◦ N, 144.801◦ E, depth: 59km, Mb (body-wave magnitude) : 7.1) and the ’visible range’ in which the epi- center can be seen from the satellite. This visible range of thesatellite, ASCA is from 12:28:15 to 12:41:15 UT on July 30, 1993, 9 days before the earthquake. Figure 3 shows the power level corresponding to this visible range. Several sharp Fig. 2. The Guam earthquake and the visible pulses are recorded in the visible range while we could not range find such responses in other visible ranges before the earth- quake. We have been able to find out some anomalies by this sys- tem. However we need to verify these responses by further studies in order to conclude these responses are associated with earthquakes. Fig. 3. S-band microwave power level during the above visible range –3– Paper Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes ∗ Takashi Maeda Student Member ∗∗ Tadashi Takano Member ∗∗ Kozaburo Inoue Non-member ∗∗ Teruo Kato Non-member Recently it was experimentally shown that rock crash by static pressure caused themicrowave emission, and this result suggests the microwave would be emitted on the occasion of earthquakes. In order to verify this hypothesis, we have developed the computer system for analyzing the huge satellite database of Institute of Space and Astronautical Science (ISAS). The databaseincludes the orbital parameters and the communi- cation data of all satellites launched by ISAS. As a result, we have found out some anomalies in the data of the S-band (2GHz) microwave power level as for ASCA satellite by this system. Keywords: seismo-electromagnetic effect, microwave emission, earthquake, satellite, data analysis system, rock crash S-band microwave power level in Section 3. Then we 1. Introduction illustrate some analysis examples in Section 4. It is reported that various anomalies of the electro- 2. Communication System between Satel- magnetic field or the ionosphere have been observed be- lites and Tracking Stations fore earthquakes. The frequency used to observe these phenomena ranges from ULF(～3Hz), ELF(3～3000Hz) Figure 1 shows theS-bandcommunication system in or VLF(3～30kHz) (1) to HF(300～3000kHz) or VHF(3～ ASCA satellite. Other satellites launched by ISAS have 300MHz) (2)–(4) .However, the microwave in GHz band similar communication system. has hardly been used. On the other hand, it was ex- There are three S-band antennas (SANT-A/B/C). In perimentally shown that rock crash by static pressure ASCA, SANT-A and SANT-B are loaded on the side caused the radio wave emission at 300MHz, 2GHz and panel and SANT-C is loaded on the bottom panel. The 22GHz (5).Thisresult suggests the microwave is emitted gain of SANT-A and SANT-B is more than -10 dBi in ◦ on the occasion of earthquakes. the range of ±80 for the direction of the antenna mast The microwaves (S-band, 2GHz) are used for the com- and that of SANT-C is more than -13 dBi in the range of ◦ munication between tracking stations and earth-orbiting ±70 for the direction of the antenna mast. Since each satellites launched by Institute of Space and Astronauti- antenna has a cardioid pattern, almost all directions are cal Science (ISAS). The S-band microwave power levels covered by these three antennas and the communication received by a satellite are stored in the database of ISAS, is ensured independently of the attitude. which is called ‘SIRIUS’. There are possibilities that the microwave emissions associated with earthquakes are de- tected in SIRIUS. Encouraged by the above circumstance, we have de- veloped the computer system to extract the S-band mi- crowave power level corresponding to major earthquakes whichoccurred all over the world from 1986 to 2004, and investigated the relation between the S-band microwave power level and earthquakes. As a result, we have been able to find out some anomalies in the data of ASCA satellite by this system. In this paper, we first show the communication system between satellites and tracking stations in Section 2 and the overview of the computer system for analyzing the ∗ Dept. of Electronics Engineering, The University of Tokyo 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 ∗∗ Institute of Space and Astronautical Science (ISAS), JAXA 3-1-1, Yoshino-dai, Sagamihara 229-8510 Fig. 1. S-band communication system in ASCA 電学論 A，126 巻 4 号，2006 年 227 In Fig. 1, dashed lines represent uplink, dotted ones Table 1. Satellites underinvestigation represent downlink, and thick ones represent status data Satellite Orbit OperationPeriod of SBR. S-band diplexers (SDIP-A/B) enable each an- GINGA Circle Feb. 5, 1987 ～ tenna to transmit and receive the S-band microwave. (530～595km) Oct. 29, 1991 Each diplexer is connected to the different S-band re- AKEBONO Ellipse Feb. 22, 1989 ～ (275～10,500km) ceiver (SBR-A/B). SBR receives the uplink the center YOHKOH Circle Aug. 30, 1991 ～ frequency of which is 2077.6 MHz ± 120 kHz. The (520～795km) Jun. 24, 2003 receiving bandwidth is determined by the bandwidth ASCA Circle Feb. 20, 1993 ～ of SBR (360 kHz) since that of each antenna is wide (525～615km) Feb. 27, 2001 HALCA Ellipse Feb. 12, 1997 ～ enough. (560～21,000km) First, the frequency of the uplink is locked by PLL (Phase Locked Loop) circuit and it is amplified by the AGC (Automatic Gain Control) in order to keep the con- stant power level, then demodulated into the command and ranging signals. The command signal is transferred to the command decoder (CMD). If the frequency chang- ing rate of the uplink is less than 20 kHz/sec, PLL is able to lock the receiving frequency. AGC is designed for amplifying the uplink from -110 dBm to -40 dBm. In order to monitor SBR status, the amplification of the AGC amplifier (this is defined as AGC level in this paper) is transferred to the data handling unit (DHU), and then converted into digital data. The sampling fre- quency of the AGC level is determined by the bit rate for constructing the telemetry data by DHU. This bit rate is any of 1024, 4096 or 32768 bps, and it is determined Fig. 2. System flowchartforextraction ofspecific by thecommand. If this bit rate is 32768 bps, the sam- satellite data pling time of the AGC level is 500 ms since it is recorded every 16 frames (1 frame = 128 words = 1024 bit). This Satellite telemetry database in SIRIUS. Based on sampled AGC level is transmitted in the downlink by database (1) and (2), the system determines the range in the S-band transmitter (TMS). which the epicenter can be seen from the satellite, which Even if the satellite is not able to communicate with is called visible range in this paper, and we extract the S- any tracking stations, SBR is always active and the AGC band microwave power level from the database (3) only level is measured and stored in the data recorder (DR). in this range on each earthquake. First, the extracting The capacity of DR is 16MByte, if the bit rate of DHU period is one month before and after an earthquake. If is 1024 bps, DR is able to recorded the data for about we can confirm anomalistic data in the period, we ex- 36 hours. This stored data is also transmitted in the pand the extracting period several years before and after downlink when the satellite is able to communicate with an earthquake. one of the tracking stations. All telemetry data received 3.2 Earthquake Database From 1986 to 2004, by the tracking stations are stored in SIRIUS. 1,480 earthquakes are recorded as historical earthquakes Therefore, the AGC level of SBR is available in or- in USGS (http://neic.usgs.gov/).
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