Most current designs of information technology are based on the notion of supporting distinct tasks such as document production, email usage, and voice communication. In this paper we present empirical results that suggest that people organize their work in terms of much larger and thematically connected units of work. We present results of fieldwork observation of information workers in three different roles: analysts, software developers, and managers. We discovered that all of these types of workers experience a high level of discontinuity in the execution of their activities. People average about three minutes on a task and somewhat more than two minutes using any electronic tool or paper document before switching tasks. We introduce the concept of working spheres to explain the inherent way in which individuals conceptualize and organize their basic units of work. People worked in an average of ten different working spheres. Working spheres are also fragmented; people spend about 12 minutes in a working sphere before they switch to another. We argue that design of information technology needs to support people's continual switching between working spheres.

[1] New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short ($1 year) observation period. We also estimate northwest motion of a coastal ''sliver block'' at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with $8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and $1 cm/yr on the Panama block-Caribbean boundary. The GPS data suggest that the Cocos plate-Panama block boundary is completely locked from $10-50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.

The Nicoya Peninsula in Costa Rica is one of the few places on Earth where the seismically active plate interface of a subduction zone is directly overlaid by land rather than ocean. At this plate interface, large megathrust earthquakes with magnitudes greater than 7 occur approximately every 50 years. Such quakes occurred in 1853, 1900 and 1950, so another large earthquake had been anticipated 1,2 . Land-based Global Positioning System 3,4 (GPS) and seismic 5-7 measurements revealed a region where the plate interface was locked and hence accumulated seismic strain that could be released in future earthquakes. On 5 September 2012, the longanticipated Nicoya earthquake occurred in the heart of the previously identified locked patch. Here we report observations of coseismic deformation from GPS and geomorphic data along the Nicoya Peninsula and show that the magnitude 7.6 Nicoya earthquake ruptured the lateral and down-dip extent of the previously locked region of the plate interface. We also identify a previously locked part of the plate interface, located immediately offshore, that may not have slipped during the 2012 earthquake, where monitoring should continue. By pairing observations of the spatial extent of interseismic locking and subsequent coseismic rupture, we demonstrate the use of detailed near-field geodetic investigations during the late interseismic period for identifying future earthquake potential.The interface between convergent plates produces most of the world's largest earthquakes, threatening local inhabitants and global populations through destructive shaking and tsunami generation, as demonstrated by the recent 2011 M w 9.0 Tohoku-Oki and 2004 M w 9.15 Sumatra-Andaman earthquakes and tsunami. Owing to the significant societal impacts, geoscientists endeavour to understand the driving and locking mechanisms controlling subduction zone seismicity. The shallow earthquakegenerating portion of the subduction interface, hereafter referred to as the megathrust, is difficult to characterize because it is relatively inaccessible, spans great lengths of continental margins and requires detailed near-field observations primarily in the marine environment.

Significance Recent destructive megathrust earthquakes and tsunamis in Japan and Sumatra indicate the difficulty of forecasting these events. Geodetic monitoring of the offshore regions of the subduction zones where these events occur has been suggested as a useful tool, but its potential has never been conclusively demonstrated. Here we show that slow slip events, nondestructive events that release energy slowly over weeks or months, are important mechanisms for releasing seismic strain in subduction zones. Better monitoring of these events, especially those offshore, could allow estimates of the size of future earthquakes and their potential for damaging tsunamis. However, the predictive value of slow slip events remains unclear.

We use campaign and continuous GPS measurements at 49 sites between 1996 and 2010 to describe the long‐term active deformation in and near the Nicoya Peninsula, northwestern Costa Rica. The observed deformation reveals partial partitioning of the Cocos‐Caribbean oblique convergence into trench‐parallel forearc sliver motion and less oblique thrusting on the subduction interface. The northern Costa Rican forearc translates northwestward as a whole ridge block at 11 ± 1 mm/yr relative to the stable Caribbean. The transition from the forearc to the stable Caribbean occurs in a narrow deforming zone of ∼16 km wide. Subduction thrust earthquakes take 2/3 of the trench‐parallel component of the plate convergence; however, surface deformation caused by interseismic megathrust coupling is primarily trench‐normal. Two fully coupled patches, one located offshore Nicoya centered at ∼15 km depth and the other located inland centered at ∼24 km depth, are identified in Nicoya with the potential to generate an Mw 7.8 1950‐type earthquake. Another fully coupled patch SE of Nicoya coincides with the rupture region of the 1990 Nicoya Gulf earthquake. Interface microearthquakes, non‐volcanic tremor, low‐frequency earthquakes, and transient slow‐slip events generally occur in the intermediately to weakly coupled regions.