Carbon dioxide emissions from dolomite decarbonation play an essential role in the weakening of carbonate faults by lowering the effective normal stress, which is thermally activated at temperatures above 600–700 °C. However, the mechanochemical effect of low-crystalline ultrafine fault gouge on the decarbonation and slip behavior of dolomite-bearing faults remains unclear. In this study, we obtained a series of artificial dolomite fault gouges with systematically varying particle sizes and dolomite crystallinities using a high-energy ball mill. The laboratory-scale pulverization of dolomite yielded MgO at temperatures below 50 °C, indicating that mechanical decarbonation without significant heating occurred due to the collapse of the crystalline structure, as revealed by X-ray diffraction and solid-state nuclear magnetic resonance results. Furthermore, the onset temperature of thermal decarbonation decreased to ∼400 °C. Numerical modeling reproduced this two-stage decarbonation, where the pore pressure increased due to low-temperature thermal decarbonation, leading to slip weakening on the fault plane even at 400–500 °C; i.e., 200–300 °C lower than previously reported temperatures. Thus, the presence of small amounts of low-crystalline dolomite in a fault plane may lead to a severely reduced shear strength due to thermal decomposition at ∼400 °C with a small slip weakening distance.An understanding of fault weakening during earthquake slip is essential to comprehend the facilitation of rupture propagation. Various mechanisms, such as flash heating (De Paola et al., 2011b), thermal pressurization (Miller et al., 2004), frictional melting (Di Toro et al., 2006), thermal decomposition (Han et al., 2007; Carpenter et al., 2015), mechanochemical changes (Hirono et al., 2013), and crystal plasticity of nanoparticles (De Paola et al., 2015; Spagnuolo et al., 2015; Violay et al., 2019), have been suggested for the reduction of frictional strength. Carbonate-bearing faults, wherein the thermal decomposition of carbonate and the resultant CO2 emissions simultaneously affect the frictional strength, merit a quantitative investigation based on mass and energy conservation laws related to pore pressure and temperature, respectively.In carbonate-bearing-faults, CO2 has been recognized as a geochemical signature of earthquake propagation (De Paola et al., 2011a; Rowe et al., 2012; Violay et al., 2013). Moreover, the relicts of decarbonation, such as degassing bubbles, vesicles, and amorphous oxide minerals, have been observed as evidence of significant heating due to coseismic slip (De Paola et al., 2011b; Collettini et al., 2013; Fondriest et al., 2013; Siman-Tov et al., 2013; Smith et al., 2013; Delle Piane et al., 2017; Ohl et al., 2020). While the decarbonation of carbonate is known to be thermally activated at ∼700 °C (Rodriguez-Navarro et al., 2012), the mechanical deformation-induced CO2 emission has also been reported in calcite (Kristóf-Makó and Juhász, 1999).Mechanical deformation processes, such as pulverization, occur extensively in slip zones (Brantut et al., 2010; Delle Piane et al., 2017; Fondriest et al., 2017), and mechanochemical changes can affect the shear strength of faults (Hirono et al., 2013). In carbonate faults, nanograins or amorphous materials are also observed in fault planes (Siman-Tov et al., 2013; Spagnuolo et al., 2015; Delle Piane et al., 2018; Ohl et al., 2020). However, the mechanochemical effect on decarbonation behavior is not fully understood from an earthquake propagation perspective.In this study, we investigated pulverized ultrafine dolomite powder, which mimics the properties of natural and artificial fault gouges, using high-energy ball mills and spectroscopy techniques for a systematic exploration of the mechanochemical effects on the strength of dolomite faults. The effects on slip behavior in dolomite faults were then quantified based on a series of thermomechanical numerical simulations.A commercial dolomite powder (SD200, SungSin, Republic of Korea) was mechanically pulverized using a high-energy ball mill (Emax, Retsch GmbH, Germany). Ultrafine dolomite particles with varying sizes and crystallinities were obtained by grinding powders for up to 480 min. During grinding, thermal heating was suppressed using a water-cooling system. The maximum temperature on the outer surface of the grinding jaw was maintained below 50 °C. The characteristics of ground dolomite were analyzed using laser diffraction particle size analysis, X-ray diffraction (XRD) spectrometry, Brunauer–Emmett–Teller specific surface area analysis, scanning electron microscopy (SEM), 25Mg solid-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetry (TG), and differential thermal analysis (DTA).To understand the effects that low-temperature (i.e., ∼400 °C) decarbonation has on the slip behavior of dolomite faults, we performed series of one-dimensional (1-D) finite element modeling (Sulem and Famin, 2009) with a 0.005 m shear zone under a seismic slip of 0.5 m/s. The depth, normal stress, and ambient temperature of the domain, considering mature carbonate faults (Rice, 2006), were 7 km, 180 MPa, and 210 °C, respectively. The phyllosilicate content of carbonate faults declines at depths >7 km (Chen et al., 2015), indicating that the frictional properties of carbonate are the main factors controlling seismic behaviors at this depth.We tested whether low-crystalline dolomite enhances CO2 emissions and shear strength weakening at low temperatures (i.e., ∼400 °C) compared with high-crystalline dolomite that exhibits decarbonation at high temperatures (i.e., ∼700 °C). A detailed description of the experimental and numerical methods is provided in the Supplemental Material1. In short, the conservation equations of mass and energy for pore pressure (Equation S7 in the Supplemental Material) and temperature (Equation S8) were coupled via a second-order Runge-Kutta time integration (So et al., 2013).The SEM images (Figs. 1A and 1B), laser diffraction particle size (Fig. 1C), and specific surface area analysis (Fig. 1D) show that the microsized dolomite particles (mean size of ∼10 μm) were pulverized into ultrafine powder (mean size of ∼0.2 μm) aggregates after grinding for 120 min. The sharp peak in the XRD pattern (Fig. 1D) gradually diminished due to the loss of crystallinity, especially for the first 120 min of grinding. The height of the primary peak (104) decreased to ∼15% compared with that observed prior to grinding (Fig. 1E), indicating the coexistence of amorphous and crystalline phases in the pulverized dolomite. The similar overall changes in the crystallinity and particle size indicated that particle size reduction and amorphization occurred simultaneously when mechanical energy was applied.The 25Mg solid-state NMR spectra showed two peaks, corresponding to Mg in dolomite [CaMg(CO3)2] at 8 ppm and periclase (MgO) at 25 ppm (Fig. 2A; Pallister et al., 2009). During grinding, the intensity of the dolomite peak gradually decreased at the expense of the periclase peak up to 120 min, indicating that dolomite partially decomposed during grinding. The loss of crystallinity and its decarbonation were found to be correlated, indicating simultaneous amorphization and decarbonation; i.e., mechanical decarbonation. Although thermal decarbonation may also partly occur due to the high local flash temperature during impact, the temperature of the grinding jaw was maintained below 50 °C during grinding. The observation that the NMR spectra clearly showed a MgO peak, which was not observed in the XRD pattern, indicates that MgO had an amorphous phase. The MgO peak observed in the as-received dolomite would have formed due to grinding of the commercial dolomite by the manufacturer. In addition, CaO and/or Ca(OH)2 can also form via mechanical decarbonation; however, this cannot be proven by the 25Mg NMR spectrum.The simultaneous occurrence of amorphization and decarbonation indicated that the level of mechanical decarbonization was related to the degree of amorphization. In this study, the formation of MgO via mechanical decarbonation proceeded to ∼30% (Fig. 2B). However, mechanical decarbonation in a fault depends on the magnitude of the mechanical energy applied to the fault zone during slip (Aretusini et al., 2017; Kaneki et al., 2020). Thus, the occurrence of mechanical decarbonization depends on the fault.The mechanochemical effects on the thermal decarbonation of dolomite were determined via TG and DTA (Figs. 2C and 2D). Thermal decarbonation can occur due to thermal heating during slip, unless the strain rate is low. Based on the endothermic reaction accompanying a weight loss of ∼47 wt% at ∼780 °C, the occurrence of single-stage thermal decarbonation in dolomite was confirmed. Upon grinding, additional low-temperature decarbonation was observed from 400 °C to 700 °C, which slightly overlapped with the high-temperature decarbonation at 700 °C. Upon grinding, the degree of low-temperature decarbonation increased, whereas that of high-temperature decarbonation decreased, indicating that high-temperature decarbonation shifted to low-temperature decarbonation with the loss of crystallinity.Low-temperature decarbonation occurred over a wider temperature range (400–700 °C) than high-temperature decarbonation (700–800 °C). These results also indicate that two-stage thermal decarbonation was induced by loss of crystallinity. Therefore, low- and high-temperature decarbonation are related to dolomite with low and high crystallinity, respectively. The physicochemical reactions of low-crystalline materials generally occur within a wider temperature range than those of high-crystalline materials because the binding energy between atoms in disordered structure varies depending on the bond length or angle. The low-temperature decarbonation possibly resulted from the lowered decarbonation temperature of the MgCO3 layer in low-crystalline dolomite, while the decarbonation temperature of the CaCO3 layer rarely changed in low-crystalline dolomite (Kristóf and Juhász, 1993). Further, the large surface area of ultrafine particles may lower the decarbonation temperature.The activation energy (Ea) of high-crystalline dolomite varies significantly between 97 and 333 kJ/mol depending on the particle size and presence of impurities (DeAngelis et al., 2007; Gunasekaran and Anbalagan, 2007). Thus, we determined that two values of Ea, i.e., 320 and 220 kJ/mol, can explain the high- and low-temperature decarbonation, respectively, observed in our laboratory experiments (Fig. S4). Temperature evolution during seismic slip strongly depends on the fraction of low-crystalline dolomite in the shear zone (Fig. 3A). The high-temperature decarbonation at ∼700 °C is clearly reproduced for the case of pure crystalline dolomite (black line). As the fraction of low-crystalline dolomite increases due to pulverization, the fraction of the phase with Ea = 220 kJ/mol also increases by up to 50%, indicating a composition of 100% low-crystalline dolomite. The temperature evolution in the shear zone shows two-stage increases of temperature and pore pressure, which are consistent with the experimental data shown in Figures 2C and 2D. In the first stage, the concentration of the low-crystalline phase does not affect the temperature increase because frictional heating dominates the thermal evolution (time ≤ 0.5 s). With further slip, the system reaches a quasi-equilibrium between frictional heating and the endothermic CO2 emission from low-crystalline dolomite.Figure 3B shows that the time and temperature at which the pore pressure in the center of the shear zone reaches ∼170 MPa are controlled by the fraction of low-crystalline dolomite. The shear zone with pure crystalline dolomite rapidly achieves a pore pressure of ∼170 MPa in a single stage after ∼2.5 s (black line). In contrast, in the presence of higher contents of low-crystalline dolomite, more time is required to reach the ∼170 MPa pore pressure in two different stages. For instance, at a concentration of 16.6% (gray line), the pore pressure reached ∼170 MPa after 9 s.Figure 3C displays the relationship between the temperature and shear strength (Equation S9). Crystalline dolomite displays a single strength drop at 650–700 °C, which is indicative of high-temperature fault weakening (black line). When low-crystalline dolomite is included, an additional abrupt drop in the shear strength is observed at 400–450 °C (blue-shaded zone) prior to high-temperature weakening at 650–700 °C (red-shaded zone). These results indicate that the presence of low-crystalline dolomite induces low-temperature thermal decomposition and fault plane weakening at ∼400 °C.The 1-D nature of our model may have prohibited off-fault fracturing (Okubo et al., 2019) during earthquake slip, inducing a permeability increase around the slip zone and resisting the buildup of pore pressure along the fault plane. We suggest that a two-dimensional model is required to account for dynamic rupture propagation due to lateral heterogeneity in the low-crystalline dolomite, as well as the off-fault fracturing.Dolomite along a fault plane is pulverized during seismic slip, affecting the occurrence of both mechanical and thermal decarbonation at a temperature lower than the typical thermal decarbonation temperature of dolomite (Fig. 4). The emission of CO2 from mechanical decarbonation results in fault weakening, which is termed fault weakening via “mechanical pressurization” (Hirono et al., 2013). The pressurization induced by thermal decomposition of pulverized dolomite can be categorized into “low-temperature pressurization” and “high-temperature pressurization” depending on the decomposition temperature, i.e., ∼400 °C and ∼700 °C, respectively. The numerical simulation results show that the presence of a small amount of low-crystalline dolomite possibly leads to significant fault weakening due to low-temperature pressurization at temperatures ∼200–300 °C lower than those previously reported. In the stage of high-temperature thermal decarbonation, the grain-size-sensitive flow (De Paola et al., 2015) activated by high temperature and small grain size may act as additional fault weakening mechanisms. The low-crystalline dolomite nanoparticles could be obliterated due to recrystallization in the presence of fluids during the interseismic period.While the presence of CaO and MgO in carbonate fault gouge has been considered as evidence of flash heating (>∼600 °C) (De Paola et al., 2011b, 2015; Fondriest et al., 2013), the latter can also occur via mechanical decarbonation; thus, the presence of CaO and MgO cannot be definitively regarded as evidence of a high-temperature environment. A previous study (Pittarello et al., 2008) suggested that >97% of the elastic strain energy is dissipated by significant frictional heating >1000 °C. However, under the regime of lower-temperature pressurization (300–500 °C), the ratio of heat dissipation to surface energy might be lower. The vigorous pressurization induced by thermal decomposition at lower temperature may lead to a larger fraction of the energy being available for creation of new surface fractures. While mechanical decarbonation has been reported in calcite (Kristóf-Makó and Juhász, 1999), the mechanochemical effects of lowering the thermal decarbonation temperature of calcite need further investigation.We thank the editor, C. Clark, and reviewers S. Aretusini, M. Violay, and an anonymous reviewer for their helpful reviews. This study was supported by the National Research Foundation (NRF) of Korea, grant NRF-2019R1F1A1061301 awarded to H. Kim, and grant NRF-2019R1A6A1A03033167 awarded to B. So. H. Kim was also supported by the “Human Resources Program in Energy Technology” from the Korea Institute of Energy Technology Evaluation and Planning, and granted financial resources from the Ministry of Trade, Industry and Energy, Republic of Korea (grant 20194010201730).

中文翻译：

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白云岩断层泥机械变形增强 CO2 加压弱化地震断层

白云岩脱碳产生的二氧化碳排放通过降低有效正应力在碳酸盐断层减弱方面发挥重要作用，有效正应力在 600-700°C 以上的温度下被热激活。然而，低晶超细断层泥对含白云岩断层脱碳和滑移行为的机械化学作用尚不清楚。在这项研究中，我们使用高能球磨机获得了一系列具有系统变化的粒度和白云岩结晶度的人工白云岩断层泥。X 射线衍射和固态核磁共振结果表明，实验室规模的白云石粉碎在低于 50 °C 的温度下产生了 MgO，表明由于晶体结构的坍塌，发生了没有明显加热的机械脱碳。此外，热脱碳的起始温度降低到~400°C。数值模拟再现了这种两阶段脱碳，其中由于低温热脱碳，孔隙压力增加，导致断层面上的滑动减弱，即使在 400-500 °C；即，比以前报告的温度低 200–300 °C。因此，断层面中少量低结晶白云岩的存在可能会导致剪切强度严重降低，因为在 400 °C 时发生热分解，滑动减弱距离很小。 了解地震滑动过程中断层减弱是必不可少的理解破裂传播的促进作用。各种机制，例如快速加热（De Paola 等，2011b）、热加压（Miller 等，2004）、摩擦熔化（Di Toro 等，2006）、热分解（Han 等，2007；Carpenter 等，2015）、机械化学变化（Hirono 等，2013）和纳米颗粒的晶体可塑性（De Paola 等，2015；Spagnuolo 等，2015； Violay 等人，2019 年），已被建议用于降低摩擦强度。含碳酸盐断层，其中碳酸盐的热分解和由此产生的 CO2 排放同时影响摩擦强度，值得分别基于与孔隙压力和温度相关的质量和能量守恒定律进行定量研究。 在含碳酸盐断层中，CO2已被认为是地震传播的地球化学特征（De Paola 等，2011a；Rowe 等，2012；Violay 等，2013）。此外，脱碳的残余物，如脱气气泡、囊泡和无定形氧化物矿物，已被观察为由于同震滑动导致显着加热的证据（De Paola 等人，2011b；Collettini 等人，2013 年；Fondriest 等人，2013 年；Siman-Tov 等人，2013 年；Smith 等人，2013 年；Delle Piane 等人，2017 年；Ohl 等人，2020 年）。虽然已知碳酸盐的脱碳在约 700 °C 时被热激活（Rodriguez-Navarro 等人，2012 年），但机械变形引起的 CO2 排放也在方解石中有所报道（Kristóf-Makó 和 Juhász，1999 年）。机械变形过程，如粉化，广泛发生在滑移带（Brantut 等，2010；Delle Piane 等，2017；Fondriest 等，2017），机械化学变化会影响断层的剪切强度（Hirono 等等，2013）。在碳酸盐断层中，在断层面中也观察到纳米颗粒或无定形材料（Siman-Tov 等人，2013 年；Spagnuolo 等人，2015年；Delle Piane 等人，2018 年；Ohl 等人，2020 年）。然而，从地震传播的角度来看，机械化学对脱碳行为的影响还没有完全理解。对白云岩断层强度的机械化学影响的系统探索。然后基于一系列热机械数值模拟量化对白云岩断层滑移行为的影响。 使用高能球磨机（Emax，Retsch GmbH，德国）机械粉碎商业白云石粉末（SD200，SungSin，韩国） ）。通过研磨粉末长达 480 分钟，可以获得具有不同尺寸和结晶度的超细白云石颗粒。在研磨过程中，使用水冷系统抑制了热量的产生。磨爪外表面的最高温度保持在 50 °C 以下。使用激光衍射粒度分析、X 射线衍射 (XRD) 光谱法、Brunauer-Emmett-Teller 比表面积分析、扫描电子显微镜 (SEM)、25Mg 固态核磁共振 (NMR) 分析了磨碎的白云石的特性光谱、热重 (TG) 和差热分析 (DTA)。为了了解低温（即~400 °C）脱碳对白云岩断层滑动行为的影响，我们进行了一系列一维（1 -D) 有限元建模（Sulem 和 Famin，2009) 在 0.5 m/s 的地震滑动下具有 0.005 m 的剪切带。考虑到成熟的碳酸盐断层（赖斯，2006 年），该域的深度、正应力和环境温度分别为 7 公里、180 兆帕和 210 °C。碳酸盐断层的页硅酸盐含量在 >7 km 深度下降（Chen et al., 2015），表明碳酸盐的摩擦特性是控制该深度地震行为的主要因素。与在高温（即~700°C）下表现出脱碳作用的高结晶白云石相比，其剪切强度在低温（即~400°C）下减弱。补充材料 1 中提供了实验和数值方法的详细说明。简而言之，孔隙压力的质量和能量守恒方程（补充材料中的方程 S7）和温度（方程 S8）通过二阶 Runge-Kutta 时间积分耦合（So 等人，2013 年）。 SEM 图像（图和图） . . 1A 和 1B）、激光衍射粒度（图 1C）和比表面积分析（图 1D）表明，微米级白云石颗粒（平均粒径为 10 μm）被粉碎成超细粉末（平均粒径为约0.2 μm) 研磨 120 分钟后聚集。由于结晶度的损失，XRD 图中的尖峰（图 1D）逐渐减弱，尤其是在研磨的前 120 分钟。与研磨前观察到的峰（图 1E）相比，主峰（104）的高度降低到约 15%，表明粉状白云石中非晶相和结晶相共存。结晶度和粒径的总体变化相似，表明当施加机械能时，粒径减小和非晶化同时发生。 25Mg 固态核磁共振谱显示两个峰，对应于白云石中的 Mg [CaMg(CO3)2] 在 8 ppm 和方镁石 (MgO) 为 25 ppm（图 2A；Pallister 等人，2009 年）。在研磨过程中，白云石峰的强度逐渐降低，但方镁石峰的强度在 120 分钟内逐渐减弱，表明白云石在研磨过程中发生了部分分解。发现结晶度的损失与其脱碳相关，表明同时发生非晶化和脱碳；即机械脱碳。尽管由于冲击过程中局部闪点温度高，也可能部分地发生热脱碳，磨削过程中，磨爪温度保持在50°C以下。NMR光谱清楚地显示出MgO峰，这在XRD图中没有观察到，这表明MgO具有非晶相。在原样白云石中观察到的 MgO 峰可能是由于制造商对商业白云石的研磨而形成的。此外，CaO 和/或 Ca(OH)2 也可以通过机械脱碳形成；然而，25Mg NMR谱不能证明这一点。非晶化和脱碳同时发生表明机械脱碳的程度与非晶化程度有关。在这项研究中，通过机械脱碳形成的 MgO 进行到 30%（图 2B）。然而，断层中的机械脱碳取决于滑动期间施加到断层带的机械能的大小（Aretusini 等人，2017 年；Kaneki 等人，2020 年）。因此，机械脱碳的发生取决于断层。对白云石热脱碳的机械化学影响是通过TG和DTA确定的（图2C和2D）。除非应变率低，否则由于滑动过程中的热加热会发生热脱碳。基于在~780°C 下伴随~47 wt% 重量损失的吸热反应，证实了白云石中单阶段热脱碳的发生。研磨时，在 400 °C 到 700 °C 之间观察到额外的低温脱碳，这与 700 °C 的高温脱碳略有重叠。研磨后，低温脱碳的程度增加，而高温脱碳的程度降低，说明高温脱碳转变为低温脱碳，结晶度下降。低温脱碳发生在更宽的温度范围（400-700 °C) 而不是高温脱碳 (700–800 °C)。这些结果还表明两阶段热脱碳是由结晶度损失引起的。因此，低温和高温脱碳分别与低结晶度和高结晶度的白云石有关。低结晶材料的物理化学反应通常发生在比高结晶材料更宽的温度范围内，因为无序结构中原子之间的结合能随键长或角度而变化。低温脱碳可能是由于低结晶白云岩中 MgCO3 层脱碳温度降低所致，而低结晶白云岩中 CaCO3 层脱碳温度变化不大（Kristóf 和 Juhász，1993）。此外，超细颗粒的大表面积可能会降低脱碳温度。 高结晶白云石的活化能 (Ea) 在 97 和 333 kJ/mol 之间显着变化，这取决于颗粒大小和杂质的存在（DeAngelis 等， 2007 年；Gunasekaran 和 Anbalagan，2007 年）。因此，我们确定 Ea 的两个值，即 320 和 220 kJ/mol，可以分别解释我们实验室实验中观察到的高温和低温脱碳（图 S4）。地震滑动过程中的温度演化很大程度上取决于剪切带中低结晶白云岩的比例（图 3A）。对于纯结晶白云石（黑线）的情况，可以清楚地再现 ~700 °C 的高温脱碳。随着粉碎导致低晶白云石的比例增加，Ea = 220 kJ/mol 的相的比例也增加了 50%，表明 100% 的低晶白云石组成。剪切带中的温度演变显示温度和孔隙压力的两阶段增加，这与图 2C 和 2D 所示的实验数据一致。在第一阶段，低结晶相的浓度不影响温度升高，因为摩擦加热主导了热演化（时间 ≤ 0.5 s）。随着进一步的滑倒，系统在摩擦加热和低结晶白云石的吸热 CO2 排放之间达到准平衡。 图 3B 显示剪切带中心孔隙压力达到 170 MPa 的时间和温度受分数控制低结晶白云石。含有纯结晶白云石的剪切带在约 2.5 秒后（黑线）在单级中迅速达到约 170 MPa 的孔隙压力。相比之下，在低结晶白云石含量较高的情况下，在两个不同阶段达到~170 MPa 孔隙压力需要更多时间。例如，当浓度为 16.6%（灰线）时，孔隙压力在 9 秒后达到 170 MPa。图 3C 显示了温度与剪切强度之间的关系（方程 S9）。结晶白云岩在 650-700 °C 时显示出单一的强度下降，这表明高温断层减弱（黑线）。当包括低结晶白云石时，在 650-700 °C（红色阴影区）高温减弱之前，在 400-450 °C（蓝色阴影区）观察到剪切强度的额外突然下降。这些结果表明，低结晶白云岩的存在会在 400 °C 时引起低温热分解和断层面减弱。我们模型的一维性质可能阻止了断层压裂（Okubo 等人，2019 年）在地震滑动过程中，导致滑动带周围渗透率增加，并抵抗沿断层平面的孔隙压力增加。我们建议需要一个二维模型来解释由于低结晶白云岩的横向非均质性以及断层压裂引起的动态破裂传播。 地震滑动过程中沿断层面的白云岩被粉碎，影响产状在低于白云石典型热脱碳温度的温度下进行机械脱碳和热脱碳（图 4）。机械脱碳排放的 CO2 导致断层减弱，这被称为通过“机械加压”的断层减弱（Hirono 等，2013）。粉状白云石热分解引起的加压根据分解温度可分为“低温加压”和“高温加压”，分别为～400℃和～700℃。数值模拟结果表明，少量低晶白云岩的存在可能会导致断层显着弱化，原因是温度低于先前报道的约 200-300°C 的低温加压。在高温热脱碳阶段，由高温和小晶粒激活的晶粒尺寸敏感流（De Paola等，2015）可能作为额外的断层弱化机制。低结晶白云石纳米颗粒可能会因地震间期流体存在下的重结晶而消失。而碳酸盐断层泥中 CaO 和 MgO 的存在被认为是快速加热（>~600 °C）的证据（De Paola 等人，2011b，2015 年；Fondriest 等人，2013 年），后者也可以通过机械脱碳发生；因此，CaO 和 MgO 的存在不能被明确地视为高温环境的证据。之前的一项研究（Pittarello 等人，2008 年）表明，> 97% 的弹性应变能被显着的摩擦热耗散了 > 1000 °C。然而，在低温加压（300-500°C）的情况下，散热与表面能的比率可能较低。在较低温度下由热分解引起的剧烈加压可能导致大部分能量可用于产生新的表面裂缝。虽然已经报道了方解石的机械脱碳作用（Kristóf-Makó 和 Juhász，1999），但降低方解石热脱碳温度的机械化学效应需要进一步研究。我们感谢编辑 C. Clark 和审稿人 S. Aretusini, M. Violay 以及一位匿名审稿人的有用评论。这项研究得到了韩国国家研究基金会 (NRF) 的支持，将 NRF-2019R1F1A1061301 授予 H. Kim，并将 NRF-2019R1A6A1A03033167 授予 B. So。H. Kim 还得到了韩国能源技术评估和规划研究所的“能源技术人力资源计划”的支持，并获得了大韩民国贸易、工业和能源部的财政资源（资助 20194010201730）。