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Intense seismicity during the 2014–15 Bárðarbunga-Holuhraun rifting event, Iceland, reveals the nature of dike-induced earthquakes and caldera collapse mechanisms
Over two weeks in August 2014 magma propagated 48km laterally from Bárðarbunga volcano before erupting at Holuhraun for 6 months, accompanied by collapse of the caldera. A dense seismic network recorded over 47,000 earthquakes before, during and after the rifting event. More than 30,000 earthquakes delineate the segmented dike intrusion. Earthquake source mechanisms show exclusively strike-slip faulting, occurring near the base of the dike along pre-existing weaknesses aligned with the rift fabric, while the dike widened largely aseismically. The slip-sense of faulting is controlled by the orientation of the dike relative to the local rift fabric, demonstrated by an abrupt change from right- to left-lateral faulting as the dike turns to propagate from an easterly to a northerly direction. Approximately 4,000 earthquakes associated with the caldera collapse delineate an inner caldera fault zone, with good correlation to geodetic observations. Caldera subsidence was largely aseismic, with seismicity accounting for 10% or less of the geodetic moment. Approximately 90% of the seismic moment release occurred on the northern rim, suggesting an asymmetric collapse. Well-constrained focal mechanisms reveal sub-vertical arrays of normal faults, with fault planes dipping inward at 60 9 , along both the north and south
caldera margins. These steep normal faults strike sub-parallel to the caldera rims, with slip vectors pointing towards the center of subsidence. The maximum depth of seismicity defines the base of the seismogenic crust under Bárðarbunga as 6km b.s.l., in broad agreement with constraints from geodesy and geobarometry for the minimum depth to the melt storage region
Carbon Free Boston: Social equity report 2019
OVERVIEW:
In January 2019, the Boston Green Ribbon Commission released its Carbon Free Boston: Summary Report, identifying potential
options for the City of Boston to meet its goal of becoming carbon neutral by 2050. The report found that reaching carbon neutrality by 2050 requires three mutually-reinforcing strategies in key sectors: 1) deepen energy efficiency while reducing energy
demand, 2) electrify activity to the fullest practical extent, and 3) use fuels and electricity that are 100 percent free of greenhouse gases (GHGs). The Summary Report detailed the ways in which these technical strategies will transform Boston’s physical
infrastructure, including its buildings, energy supply, transportation, and waste management systems. The Summary Report also
highlighted that it is how these strategies are designed and implemented that matter most in ensuring an effective and equitable transition to carbon neutrality.
Equity concerns exist for every option the City has to reduce GHG emissions. The services provided by each sector are not
experienced equally across Boston’s communities. Low-income families and families of color are more likely to live in residences that are in poor physical condition, leading to high utility bills, unsafe and unhealthy indoor environments, and high GHG
emissions.1
Those same families face greater exposure to harmful outdoor air pollution compared to others. The access and
reliability of public transportation is disproportionately worse in neighborhoods with large populations of people of color, and
large swaths of vulnerable neighborhoods, from East Boston to Mattapan, do not have ready access to the city’s bike network.
Income inequality is a growing national issue and is particularly acute in Boston, which consistently ranks among the highest US
cities in regards to income disparities. With the release of Imagine Boston 2030, Mayor Walsh committed to make Boston more
equitable, affordable, connected, and resilient. The Summary Report outlined the broad strokes of how action to reach carbon
neutrality intersects with equity. A just transition to carbon neutrality improves environmental quality for all Bostonians, prioritizes socially vulnerable populations, seeks to redress current and past injustice, and creates economic and social opportunities
for all.
This Carbon Free Boston: Social Equity Report provides a deeper equity context for Carbon Free Boston as a whole, and for
each strategy area, by demonstrating how inequitable and unjust the playing field is for socially vulnerable Bostonians and why
equity must be integrated into policy design and implementation. This report summarizes the current landscape of climate
action work for each strategy area and evaluates how it currently impacts inequity. Finally, this report provides guidance to the
City and partners on how to do better; it lays out the attributes of an equitable approach to carbon neutrality, framed around
three guiding principles: 1) plan carefully to avoid unintended consequences, 2) be intentional in design through a clear equity
lens, and 3) practice inclusivity from start to finish
An Analysis of Community Choice Energy for Boston
Community Choice Energy (CCE) allows a municipality to purchase electricity from a competitive supplieron behalf of participating electric customers. CCE would allow Boston to pool customers together, using this greater bargaining power to benefit customers in the City. In addition, through CCE, the City would purchase at least five percent more Class I renewable energy than required under the Commonwealth'sRenewable Energy Portfolio (RPS) law.Currently, 127 cities and towns Massachusetts have adopted CCE—more than one-third of the 351 municipalities in the Commonwealth. Many municipalities that implement CCE procure five percent more renewable energy than is required by the Massachusetts RPS. Some are going even further, such as Brookline, which is purchasing 25 percent more renewable energy than required, and Greenfield, which is purchasing 100 percent renewables.This report reviews commonly asked questions that the City should consider as it assesses whether to adopt this policy