Contents． 1
Papers and Reports． 1
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1．M．TSSUJIURA,Activity Mode of the 1980 Earthquake Swarm off the East Coast of the Izu Peninsula．(in English) 1
2．T．UTSU,Seismicity of the Izu Peninsula and Its Vicinity from 1901 through 1980 with Some Remarks on the Characteristics of Foreshock Activities．(in English) 25
3．T．OUCHI,S．NAGUMO and S．KORESAWA,Ocean Bottom Seismometer Study on the Seismic Activity in the Mariana Island Arc Region．(in English) 43
4．M．OHNAKA and K．MOGI,Frequency Dependence of Acoustic Emission Activity in Rocks under Incremental,Uniaxial Compression．(in English) 67
5．H．FUJISAWA,K．KURITA and H．KINOSHITA,A New Method of the Measurement of Ultrasonic Wave Velocity of Solids under High Pressures up to 40 Kilobars(Part Ⅰ)．(in English) 91
6．T．HATORI,Tsunami Magnitude and Source Area of the Aleutian-Alaska Tsunamis．(in English) 97
7．T．UTSU,Seismicity of Central Japan from 1904 through 1925．(in,Japanese) 111
8．M．MIZOUE,I．NAKAMURA,H．CHIBA,M．YOSHIDA,H．HAGIWARA and ？ YOKOTA,The Structure of the Upper Part of the Crust in the Regions of Saaga？ Bay,the Izu Peninsula and Suruga Bay as Found by the Observation of the arthquake Swarm East off the Izu Peni 139
9．M．SAITOH and J．KASAHARA,Acquisition System of Airgun Firing Data Using Microprocessors．(in Japanese) 161
10．J．KASAHARA,Time Code Reader for Ocean Bottom Seismometer Using Micro-processor and Its Application for New Data Processing．(in Japanese) 195
11．J．KASAHARA,S．KORESAWA and Y．NISHI,Preliminary Report for Large Bottom Current at the Deep Ocean FloorInferred from Ocean Bottom Seismic Observations．(in Japanese) 207
12．T．YUKUTAKE,T．YOSHINO,H．UTADA,M．KAWAMURA,K．OCHI,Y．MIZUNO,K．KOIKE and M．KOSUGA,Distribution of Electrical Resistivity and Geomagnetic Field Components in the Zy？dodaira Area of Azumasan Volcano．(in Japanese) 223
13．T．HATORI,I．AIDA,S．IWASAKI and T．HIBIYA,Field Survey of the Tsunamis Inundating Owase City—The 1944 Tonankai,1960 Chile,and 1854 Ansei Tsunamis．(in Japanese) 245
14．E．SHIMA,M．YANAGISAWA,K．KUDO and K．SEO,On the Base Rock of Tokyo．V．Observations of Seismic Waves Generated from the 7th,8th and 9th Yumenoshima Explosions．(in Japanese) 265
15．T．ODAKA,Ray-Theoretical Approach to Frequency Equations of Spheroidal Oscillations of a Spherical Earth with Uniform or Non-Uniform Mantle and Core．(in English) 277
16．T．MAKI,Regional Variation of Pn Residuals and Its Application to the Location of Earthquakes in and around the Kanto District．(in English) 309
17．K．KODAMA,A Paleomagnetic Reconnaissance of the Bonin Islands．(in English) 347
18．I．AIDA,Numerical Experiments of Historical Tsunamis Generated off the Coast of the Tokaido District．(in Japanese) 367
19．T．MIYAZAK,N．GYODA and S．HIRAGA,The Seismic Activity of Mt．Fuji Volcano．(in Japanese) 391