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Illegal, unreported, and unregulated (IUU) fishing is becoming a growing threat to sustainable fisheries and the economy worldwide. To solve this issue, various efforts on monitoring, control, and surveillance (MCS) have been made at the national, regional, and international levels. However, there is still the lack of measures against IUU fishing vessels at the multilateral level. Here, we assessed the situations of fisheries, and the current systems and challenges of MCS in eight Asia-Pacific countries with a focus on MCS of IUU fishing vessels at sea. Through a literature review and interviews, we confirmed that IUU fishing was linked with the status of fisheries in each country, and that each country implements various MCS measures with different emphases. However, there was a trend of enhancing or newly establishing four areas of MCS: vessel tracking, patrol, onboard observers, and port State measures, with amended or newly adopted laws. We also identified challenges of MCS such as insufficient MCS in coastal areas and fragmented cooperation among the countries. Based on our findings, we advance several recommendations including the enhancement of cooperation among stakeholders, especially fishers, for co-monitoring in coastal areas and the establishment of a communication platform for Asia-Pacific countries.

The three-dimensional (3-D) velocity structure of the upper crust in the central part of the Hida region, central Honshu, Japan, has been investigated by simultaneous inversion of travel time data for velocity and hypocentral parameters using Thurber's method (1983). The data used for this purpose were 2, 231 P-wave arrival times from 204 local earthquakes observed at 16 high-sensitivity seismograph stations. The iterative damped least-squares inversion used here provided reliable results with the diagonal elements of resolution matrix well exceeding 0.90 and standard errors less than 3% for the central area. The central part of the Hida region covering an extremely low seismicity area has high velocities probably extending down to a mid-crust. The high-velocity area composed of hard metamorphic and granitic complex extends from the western flank of the Hida mountains to the western section of the seismically active Atotsugawa-Ushikubi faults. The axial part of the Hida mountains and its southwestward area, on the other hand, is covered by remarkable low-velocities. The low velocities may be associated with a high thermal state due to active volcanism beneath the mountains involving volcanoes Mts. Tateyama, Yake, Norikura, and Ontake. The southwestern part of the Hida region is also partially covered by low-velocities beneath the Ryohaku mountains, which may also be related to volcanism of Mt. Hakusan. The obtained 3-D velocity structure appears to be qualitatively consistent with the Bouguer gravity anomalies and also with the large-scale 3-D structure so far obtained.

Focal mechanisms around Ontake Volcano, central Japan, were investigated by using the data set obtained by a seismic observation project of the 1986 Joint Seismological Research in Western Nagano Prefecture (JSR'86). The data set included P-wave first motions of aftershocks of the 1984 Western Nagano Prefecture Earthquake (M=6.8) mainly. A total of 556 events was selected for the focal mechanism analysis. The P-wave data from the surrounding university routine networks were also utilized additionally. Four hundred two events were successfully analyzed. Based on the types of focal mechanisms and on the spatial distribution of the events, we classify these events into the following 4 groups: (1) events of strike-slip fault type with a common nodal plane parallel to the ENE-WSW striking nodal plane in the fracture zone of the 1984 main shock; (2) events of reverse fault type in the area of the preexisting earthquake swarm to the northeast of the main shock, in a possible relation with an earthquake swarm activated by the main shock; (3) events of reverse fault type that occurred near the largest aftershock (M=6.2), but are not the continued aftershock sequence of the largest aftershock; (4) events of strike-slip fault type at depths to the easternmost part where no activity had been observed before the operation of JSR'86. The plural types of focal mechanisms obtained and the spatial distribution of foci suggest a complex seismo-tectonic structure that consists of at least 2 kinds of fracturings around Ontake Volcano.

A dense temporary seismograph network was set up in the aftershock area of the 1984 Western Nagano Prefecture Earthquake of M 6.8 by the group for the 1986 Joint Seismological Research in Western Nagano Prefecture. Seismograms of about 1,500 events were obtained during the observation period of 52 days from September 1 to October 22, 1986, and 530 events in and around the aftershock area were located precisely. Extent of the aftershock area is about 20 km in the east-west and about 7 km in the north-south.

The detailed three-dimensional P and S wave velocity structure in the focal region of the 1984 Western Nagano Prefecture Earthquake occurring close to an active volcano, Mt. Ontake, central Japan, is derived from a tomographic inversion of travel time data obtained by the 1986 Joint Seismological Research in Western Nagano Prefecture. The data set includes 7, 693 P-wave and 6, 070 S-wave arrival times observed at 49 stations from 212 local earthquakes and 2 explosions. The velocities in the shallow portion of upper crust are determined at each grid point with its spacing of 1-2 km and good resolutions are obtained from the Earth's surface to a depth of 4 km. There exist strong lateral heterogeneities especially from the surface to a depth of 1 km. The seismic velocity map obtained in the height of 1 km above sea level well corresponds to the maps of surface geology and Bouguer gravity anomaly. This correspondence, however, is not so clear in the deeper layers. And, the greater the depth, the less heterogeneous the velocity structure. The velocity distribution on the fault seems to correspond to the distribution of dislocation and rupture front estimated from an analysis of strong motion and geodetic data: the low velocity region has the large amount of dislocation and the retarded rupture front.

Radon alpha tracks monitored at six sites increased gradually three months before (detected by microscopic counting), and increased remarkably 2 weeks before (detected by both mechanical and microscopic counting) the western Nagano Prefecture earthquake (M 6.8) which occurred on September 14, 1984. The monitoring sites were located about 65 km northwest of the epicenter, on the shear zone of the Atotsugawa fault. The changes in radon emanation are considered to be related to the earthquake rather than to changes in meteorological conditions.

Real-time exchange of waveform data from neighboring seismograph networks is significantly advancing seismic monitoring in central Japan. Five observation centers are connected by leased circuits from NTT (Nippon Telegraph and Telephone Corporation), to exchange three to nine channels of seismic signals on a routine basis. Detection capability and accuracy of seismic parameters for events near network boundaries are considerably improved with this system. It can fill the observation gaps between networks, as verified at the Izu Peninsula and the Hida region, central Japan. Monitoring of seismic activity in the Izu Peninsula, for example, is greatly improved. By connecting local networks in this way, a regional observation system for microearthquakes has been established in central Japan.